Arizona: Individual County Chronologies
Arizona Atlas of Historical County Boundaries
John H. Long, Editor; Peggy Tuck Sinko, Associate Editor; Emily Kelley, Historical Compiler; Laura Rico-Beck
GIS Specialist and Digital Compiler; Peter Siczewicz, ArcIMS Interactive Map Designer; Robert
Will, Cartographic Assistant
Copyright The Newberry Library 2007
14 Feb 1879 APACHE created by Arizona Territory from YAVAPAI. (Ariz. Terr. Laws 1879, 10th assy./ pp. 96-97)
10 Mar 1881 APACHE lost to creation of GRAHAM. (Ariz. Terr. Laws 1881, 11th assy./ pp. 155-157)
21 Mar 1895 APACHE lost to creation of NAVAJO. (Ariz. Terr. Laws 1895, 18th assy./ pp. 96-105)
17 Mar 1897 Boundary between APACHE and GRAHAM clarified [no change]. (Ariz. Terr. Laws 1897, 19th assy./ p. 67)
ARIZONA (N.M. Territory, extinct)
01 Feb 1860 ARIZONA (N.M. Territory, extinct) created by New Mexico Territory from
DOÑA ANA (N.M.). ARIZONA (extinct) was located entirely within present
Arizona. (N.M. Terr. Laws 1859-1860, 9th assy. /p. 74)
18 Jan 1862 ARIZONA (N.M. Territory, extinct) eliminated when it lost all territory to DOÑA
ANA. (N.M.). (N.M. Terr. Laws 1861-1862, 11th assy. /p. 18)
28 Jan 1863 ARIZONA (N.M. Territory, extinct) re-created from DOÑA ANA (N.M.). (N.M.
Terr. Laws 1862-1863, 12th assy. /p.30)
24 Feb 1863 ARIZONA (N.M. Territory, extinct) eliminated when Arizona Territory was
created from New Mexico Territory. (U.S. Stat., vol. 12, ch. 56[1863]/pp.
664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt, 162)
Arizona Territory (non-county area)
24 Feb 1863 Arizona Territory created by the United States from the western portion of New
Mexico Territory and a part of present Nevada. Arizona did not immediately
create any counties. BERNALILLO (N.M.), DOÑA ANA (N.M.), RIO ARRIBA
(N.M.), SANTA ANA (N.M. Territory, extinct), SOCORRO (N.M.), TAOS (N.M.)
and VALENCIA (N.M.) all eliminated from Arizona Territory, ARIZONA (N.M.
Territory, extinct) eliminated entirely. (U.S. Stat., vol. 12, ch. 56[1863]/pp.
664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt, 162)
05 May 1866 Arizona Territory lost parts of MOHAVE and PAH-UTE (extinct) when the
United States transferred the portion of Arizona Territory lying between 37
degrees and 42 degrees of north latitude and west of 114 degrees west
longitude to the state of Nevada. Arizona twice petitioned Congress (5 May
1866 and 5 October 1867) to repeal the act of transfer and did not officially
recognize the loss until 18 February 1871 when a change to the boundaries
of MOHAVE implicitly acknowledged the new Arizona - Nevada line. (U.S. Stat.,
vol. 14, ch. 73[1866]/p. 43; Van Zandt, 158, 165; Ariz. Terr. Laws 1867, 3rd
assy./ pp. 67-68; Ariz. Terr. Laws 1868, 4th assy./ pp. 68-69)
22 Sep 1846 BERNALILLO (N.M.) established as one of seven original New Mexico
counties under Kearny's Code of Laws for the occupied Mexican territory;
located entirely in New Mexico [not mapped]. (Kearny's Code 1846, "Courts
and Judicial Powers", secs. 5-7/p. 49; Abel, Map #2; Coan, 252; Williams, 108-109)
09 Jan 1852 BERNALILLO (N.M.) gained from VALENCIA (N.M.) and non-county area,
exchanged with SAN MIGUEL (N.M.), and lost to SANTA ANA (N.M.) and
SANTA FE (N.M.) when all counties redefined; included parts of present
Arizona, Nevada and New Mexico. (N.M. Terr. Laws 1851, 1st assy., 2d sess.
/p. 292)
24 Feb 1863 BERNALILLO (N.M.) eliminated from Arizona when Arizona Territory was
created from the western portion of New Mexico Territory. (U.S. Stat., vol. 12,
ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van
Zandt, 162)
05 Apr 1860 An unofficial convention held in Tucson established a provisional government,
declared the creation of the Territory of Arizona from all that part of New
Mexico Territory that lay south of 33 degrees 40 minutes north latitude, and
authorized the creation of CASTLE DOME (proposed). Congress failed to
recognize the new territory and its proposed counties [no change]. (Sacks, 36,
151; Swindler, 1:244-248)
01 Feb 1881 COCHISE created by Arizona Territory from PIMA. (Ariz. Terr. Laws 1881,
11th assy./ pp. 4-7)
11 Feb 1935 COCHISE boundaries redefined [no change]. (Ariz. Laws 1935, 12th reg.
sess., ch. 7/p. 11)
14 Mar 1968 COCHISE gained from SANTA CRUZ when the boundary was redefined to
run along the east line of range 18 east. (Ariz. Laws 1968, 28th leg., 1st reg.
sess., ch. 82/ pp. 180-182)
19 Feb 1891 COCONINO created by Arizona Territory from YAVAPAI. (Ariz. Terr. Laws
1891, 16th assy./ pp. 26-34)
13 Dec 1850 Faulty geographic information on the Disturnell map referenced in the Treaty
of Guadalupe-Hidalgo led to a dispute between the United States and Mexico
over the exact location and extent of the international boundary. Map shows
only the part of Disputed Area in present Arizona. (U.S. Stat., vol. 9, ch.
49[1850]/pp. 446-452; Baldwin, 117-137; Coffey, 145-164; Van Zandt, 28-29,
162-165)
09 Jan 1852 Dispute between the United States and Mexico over the exact location and
extent of the international boundary continued. Map shows the entire Disputed
Area. (U.S. Stat., vol. 9, ch. 49[1850]/pp. 446-452; Baldwin, 117-137; Coffey,
145-164; Van Zandt, 28-29, 162-165)
30 Dec 1853 Gadsden Purchase settled the boundary dispute between the United States
and Mexico and established the international line at its present location;
Disputed Area eliminated. (U.S. Stat., vol. 10, pp. 1031-1037; Van Zandt,
11, 29, 162)
09 Jan 1852 DOÑA ANA (N.M.) created by New Mexico Territory from non-county area;
included parts of present Arizona and New Mexico. (N.M. Terr. Laws 1851, 1st
assy., 1st sess./p. 119; N.M. Terr. Laws 1851, 1st assy., 2d sess. /pp. 266,
292)
03 Feb 1855 DOÑA ANA (N.M.) gained all of non-county area (Gadsden Purchase) in New
Mexico Territory; non-county area eliminated. (N.M. Terr. Laws 1854, 4th assy.
/p. 57)
01 Feb 1860 DOÑA ANA (N.M.) lost to creation of ARIZONA (N.M. Territory, extinct). (N.M.
Terr. Laws 1859-1860, 9th assy. /p. 74)
18 Jan 1862 DOÑA ANA (N.M.) gained all of ARIZONA (N.M. Territory, extinct); ARIZONA
eliminated. (N.M. Terr. Laws 1861-1862, 11th assy. /p. 18)
28 Jan 1863 DOÑA ANA (N.M.) lost to re-creation of ARIZONA (N.M. Territory, extinct).
(N.M. Terr. Laws 1862-1863, 12th assy. /p.30)
24 Feb 1863 DOÑA ANA (N.M.) eliminated from Arizona when Arizona Territory was
created from the western portion of New Mexico Territory. (U.S. Stat., vol. 12,
ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van
Zandt, 162)
05 Apr 1860 An unofficial convention held in Tucson established a provisional government,
declared the creation of the Territory of Arizona from all that part of New
Mexico Territory that lay south of 33 degrees 40 minutes north latitude, and
authorized the creation of DOÑA ANA (proposed). Congress failed to
recognize the new territory and its proposed counties [no change]. (Sacks, 36,
151; Swindler, 1:244-248)
05 Apr 1860 An unofficial convention held in Tucson established a provisional government,
declared the creation of the Territory of Arizona from all that part of New
Mexico Territory that lay south of 33 degrees 40 minutes north latitude, and
authorized the creation of EWELL (proposed). Congress failed to recognize
the new territory and its proposed counties [no change]. (Sacks, 36, 151;
Swindler, 1:244-248)
30 Dec 1853 Gadsden Purchase settled the boundary dispute between the United States
and Mexico and established the international line at its present location. (U.S.
Stat., vol. 10, pp. 1031-1037; Van Zandt, 11, 29, 162)
04 Aug 1854 Area acquired in the Gadsden Purchase became non-county area when it was
officially added to New Mexico Territory without being assigned to a county.
(U.S. Stat., vol. 10, ch. 245[1854]/p. 575; Van Zandt, 162; Walker and Bufkin,
2 1-22)
08 Feb 1881 GILA created by Arizona Territory from MARICOPA and PINAL. (Ariz. Terr.
Laws 1881, 11th assy./ pp. 14-17)
12 Mar 1885 GILA exchanged with GRAHAM. (Ariz. Terr. Laws 1885, 13th assy./ p. 215)
21 Mar 1889 GILA gained from YAVAPAI. (Ariz. Terr. Laws 1889, 15th assy./ pp. 49-52)
19 Mar 1891 GILA gained from YAVAPAI. (Ariz. Terr. Laws 1891, 16th assy./ pp. 102-103)
10 Mar 1881 GRAHAM created by Arizona Territory from APACHE and PIMA. (Ariz. Terr.
Laws 1881, 11th assy./ pp. 155-157)
12 Mar 1885 GRAHAM exchanged with GILA. (Ariz. Terr. Laws 1885, 13th assy./ p. 215)
17 Mar 1897 Boundary between GRAHAM and APACHE clarified [no change]. (Ariz. Terr.
Laws 1897, 19th assy./ p. 67)
10 Mar 1909 GRAHAM lost to creation of GREENLEE. (Ariz. Terr. Laws 1909, 25th assy./ pp. 43-56)
10 Mar 1909 GREENLEE created by Arizona Territory from GRAHAM. (Ariz. Terr. Laws
1909, 25th assy./ pp. 43-56)
27 Apr 1983 LA PAZ created from YUMA. (Ariz. Laws 1983, 36th assy., ch. 291/pp.
1089-1094)
14 Feb 1871 MARICOPA created by Arizona Territory from YAVAPAI. (Ariz. Terr.
Laws 1871, 6th assy./ pp. 53-54)
14 Feb 1873 MARICOPA gained from PIMA. (Ariz. Terr. Laws 1873, 7th assy./ p. 87)
01 Feb 1875 MARICOPA lost to creation of PINAL. (Ariz. Terr. Laws 1875, 8th assy./ pp.
19-20)
31 Jan 1877 MARICOPA gained from YAVAPAI, and lost small area along the Gila River to
PIMA. (Ariz. Terr. Laws 1877, 9th assy./ pp. 12-13)
08 Feb 1881 MARICOPA lost to creation of GILA. (Ariz. Terr. Laws 1881, 11th assy./ pp.
14-17)
05 Apr 1860 An unofficial convention held in Tucson established a provisional government,
declared the creation of the Territory of Arizona from all that part of New
Mexico Territory that lay south of 33 degrees 40 minutes north latitude, and
authorized the creation of MESILLA (proposed). Congress failed to recognize
the new territory and its proposed counties [no change]. (Sacks, 36, 151;
Swindler, 1:244-248)
24 Aug 1821 Mexico gained its independence from Spain; present Arizona became part of
the Republic of Mexico. (Beers, 100; "Mexican War of Independence," New
Handbook of Texas, 4:698)
04 Jul 1848 Treaty of Guadalupe-Hidalgo ended the war between Mexico and the United
States. Area ceded by Mexico became Unorganized Federal Territory in the
United States; included all of present California, Nevada, and Utah, and parts
of present Arizona, Colorado, New Mexico, and Wyoming. Mexico retained
parts of present Arizona and New Mexico; Part of the international boundary
was in dispute. Map shows only the part of Mexico in present Arizona. (U.S.
Stat., vol. 9, pp. 922-943; Parry, 102: 29-59; Van Zandt, 11, 28-29; Walker and
Bufkin, 19, 20A)
13 Dec 1850 The portion of present Arizona located south of the boundary defined in the
Treaty of Guadalupe-Hidalgo was part of Mexico. Faulty geographic
information on the Disturnell map referenced in the treaty led to a dispute
between the United States and Mexico over the exact location and extent of
the international boundary. Map shows only the part of Mexico in present
Arizona. (U.S. Stat., vol. 9, ch. 49[1850]/pp. 446-452; Baldwin, 117-137;
Coffey, 145-164; Van Zandt, 28-29, 162-165)
09 Jan 1852 The parts of present Arizona and New Mexico located south of the boundary
defined in the Treaty of Guadalupe-Hidalgo were part of Mexico; dispute
between the United States and Mexico over the exact location and extent of
the international boundary continued. (U.S. Stat., vol. 9, ch. 49[1850]/pp.
446-452; Baldwin, 117-137; Coffey, 145-164; Van Zandt, 28-29, 162-165)
30 Dec 1853 Gadsden Purchase settled the boundary dispute between the United States
and Mexico and established the international line at its present location. (U.S.
Stat., vol. 10, pp. 1031-1037; Van Zandt, 11, 29, 162)
10 Nov 1864 MOHAVE created as one of four original counties in Arizona Territory;
included part of present Nevada. (Howell Code, Ariz. Terr. Laws 1864, 1st
assy., ch. 2/ pp. 24-25)
22 Dec 1865 MOHAVE lost to creation of PAH-UTE (extinct). (Ariz. Terr. Laws 1865, 2d
assy./ pp. 19-20)
05 May 1866 MOHAVE lost when the United States transferred a portion of northwestern
Arizona Territory to the state of Nevada. Arizona twice petitioned Congress to
repeal the act and did not recognize the change until 18 February 1871. (U.S.
Stat., vol. 14, ch. 73[1866]/p. 43; Sacks, 25; Van Zandt, p. 158, 165)
18 Feb 1871 MOHAVE gained all of PAH-UTE (extinct) when the law creating PAH-UTE
was repealed. New definition for MOHAVE implicitly acknowledged the
change made to the Arizona - Nevada line on 5 May 1866. (Ariz. Terr. Laws
1871, 6th assy./ p. 87)
06 Mar 1883 MOHAVE exchanged with YAVAPAI. (Ariz. Terr. Laws 1883, 12th assy./ p. 171)
24 Mar 1960 MOHAVE boundary with the state of Nevada was redefined as part of an
interstate compact to account for changes in the course of the Colorado River.
The adjusted state line apparently had a minor effect on the boundary
between MOHAVE and CLARK (Nevada) [not mapped]. (Ariz. Laws 1960,
24th leg., 2d reg. sess., ch. 69/pp. 174-180)
02 Apr 1963 MOHAVE boundary with the state of California was redefined as part of an
interstate compact to account for changes in the course of the Colorado River
[not mapped]. (Ariz. Laws 1963, 25th leg., 1st reg. sess., ch. 77/ pp. 142-150)
21 Mar 1895 NAVAJO created by Arizona Territory from APACHE. (Ariz. Terr. Laws
1895, 18th assy./ pp. 96-105)
New Mexico Territory (non-county area)
13 Dec 1850 The United States created New Mexico Territory from Unorganized Federal
Territory (land ceded by Mexico in the Treaty of Guadalupe-Hidalgo), and from
land purchased from the state of Texas; included most of present Arizona and
New Mexico, and parts of present Colorado and Nevada. Faulty geographic
information on the Disturnell map referenced in the treaty led to a dispute
between the United States and Mexico over the exact location and extent of
the international boundary. All that portion of New Mexico Territory lying
outside the boundaries of the seven original counties established under
Kearny's Code became non-county area; included most of present Arizona
and New Mexico, and parts of present Colorado and Nevada. The portion of
Arizona south of the Gila River remained part of Mexico. Maps shows only the
part of New Mexico Territory in present Arizona and Nevada. (U.S. Stat., vol.
9, ch. 49[1850]/pp. 446-452; Baldwin, 117-137; Coffey, 145-164; Van Zandt,
28-29, 162-165)
09 Jan 1852 Non-county area in New Mexico lost to creation of DOÑA ANA (N.M.) and
SOCORRO (N.M.), and lost to BERNALILLO (N.M.), RIO ARRIBA (N.M.),
SAN MIGUEL (N.M.), SANTA ANA (N.M.), TAOS (N.M.), and VALENCIA
(N.M.); all included part of present Arizona; Non-county area eliminated. (N.M.
Terr. Laws 1851, 1st assy., 2d sess. /p. 291)
04 Aug 1854 Non-county area was created in New Mexico Territory when the land acquired
by the United States in the Gadsden Purchase was officially added to the
territory without being assigned to a county. Most of the non-county area was
located in present Arizona. (U.S. Stat., vol. 10, ch. 245[1854]/p. 575; Van
Zandt, 162; Walker and Bufkin, 21-22)
03 Feb 1855 Non-county area in New Mexico Territory lost to DONA ANA (N.M.); Non-
county area eliminated. (N.M. Terr. Laws 1854, 4th assy. /p. 57)
22 Dec 1865 PAH-UTE (extinct) created by Arizona Territory from MOHAVE; included part
of present Nevada. (Ariz. Terr. Laws 1865, 2d assy./ pp. 19-20)
05 May 1866 PAH-UTE (extinct) lost when the United States transferred a portion of
northwestern Arizona Territory to the state of Nevada. Arizona twice petitioned
Congress to repeal the act and did not recognize the change until 18 February
1871. (U.S. Stat., vol. 14, ch. 73[1866]/p. 43; Sacks, 25; Van Zandt, p. 158,
165)
18 Feb 1871 PAH-UTE (extinct) lost all territory to MOHAVE when the law creating PAH-
UTE was repealed; PAH-UTE eliminated. (Ariz. Terr. Laws 1871, 6th assy./ p.
87)
10 Nov 1864 PIMA created as one of four original counties in Arizona Territory. (Howell
Code, Ariz. Terr. Laws 1864, 1st assy., ch. 2/ pp. 24-25)
14 Feb 1873 PIMA lost to MARICOPA. (Ariz. Terr. Laws 1873, 7th assy./ p. 87)
01 Feb 1875 PIMA lost to creation of PINAL and was divided into two parts until 9 February
1877. (Ariz. Terr. Laws 1875, 8th assy./ pp. 19-20)
31 Jan 1877 PIMA gained a small area along the Gila River from MARICOPA. (Ariz. Terr.
Laws 1877, 9th assy./ pp. 12-13)
09 Feb 1877 PIMA lost to PINAL. Area lost was the part of PIMA that had been separated
from main body of the county on 1 February 1875. (Ariz. Terr. Laws 1877, 9th
assy./ pp.108-109)
01 Feb 1881 PIMA lost to creation of COCHISE. (Ariz. Terr. Laws 1881, 11th assy./ pp. 4-7)
10 Mar 1881 PIMA lost to creation of GRAHAM. (Ariz. Terr. Laws 1881, 11th assy./ pp.
155-157)
15 Mar 1899 PIMA lost to creation of SANTA CRUZ. (Ariz. Terr. Laws 1899, 20th assy./ pp.
49-57)
02 May 1973 PIMA boundaries redefined [no change]. (Ariz. Laws 1973, 31st leg., 1st reg.
sess., ch. 101/ pp. 596-597)
01 Feb 1875 PINAL created by Arizona Territory from MARICOPA and PIMA. (Ariz. Terr.
Laws 1875, 8th assy./ pp. 19-20)
09 Feb 1877 PINAL gained from PIMA. Area gained was the part of PIMA that had been
separated from main body of the county on 1 February 1875. (Ariz. Terr. Laws
1877, 9th assy./ pp. 108-109)
08 Feb 1881 PINAL lost to creation of GILA. (Ariz. Terr. Laws 1881, 11th assy./ pp. 14-17)
22 Sep 1846 RIO ARRIBA (N.M.) established as one of seven original New Mexico
counties under Kearny's Code of Laws for the occupied Mexican territory;
located entirely in New Mexico [not mapped]. (Kearny's Code 1846, "Courts
and Judicial Powers", secs. 5-7/p. 49; Abel, Map #2; Coan, 252; Williams,
108-109)
09 Jan 1852 RIO ARRIBA (N.M.) gained from SAN MIGUEL (N.M.), SANTA ANA (N.M.),
SANTA FE (N.M.) and non-county area, and exchanged with TAOS (N.M.)
when all counties redefined; included parts of present Arizona, Nevada and
New Mexico. (N.M. Terr. Laws 1851, 1st assy., 2d sess. /p. 291)
24 Feb 1863 RIO ARRIBA (N.M.) eliminated from Arizona when Arizona Territory was
created from the western portion of New Mexico Territory. (U.S. Stat., vol.12,
ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van
Zandt, 162)
SAN JUAN (N.M. Territory, original, extinct)
12 Jan 1861 SAN JUAN (N.M. Territory, original, extinct) created by New Mexico Territory
from TAOS (N.M.); included parts of present Arizona, New Mexico, and
Nevada. (N.M. Terr. Laws 1860-1861, 10th assy. /p. 16)
18 Jan 1862 SAN JUAN (N.M. Territory, original, extinct) eliminated when it lost all territory
to TAOS (N.M.)
SANTA ANA (N.M. Territory, extinct)
22 Sep 1846 SANTA ANA (N.M. Territory, extinct) established as one of seven original New
Mexico counties under Kearny's Code of Laws for the occupied Mexican
territory; located entirely in New Mexico [not mapped]. (Kearny's Code 1846,
"Courts and Judicial Powers", secs. 5-7/p. 49; Abel, Map #2; Coan, 252;
Williams, 108-109)
09 Jan 1852 SANTA ANA (N.M. Territory, extinct) gained from BERNALILLO (N.M.) and
non-county area, exchanged with SANTA FE (N.M.), and lost to RIO ARRIBA
(N.M.) when all counties redefined; included parts of present Arizona, Nevada,
and New Mexico. (N.M. Terr. Laws 1851, 1st assy., 2d sess. /p. 292)
24 Feb 1863 SANTA ANA (N.M. Territory, extinct) eliminated from Arizona when Arizona
Territory was created from the western portion of New Mexico Territory. (U.S.
Stat., vol. 12, ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp.
vii-viii; Van Zandt, 162)
15 Mar 1899 SANTA CRUZ created by Arizona Territory from PIMA. (Ariz. Terr. Laws 1899,
20th assy./ pp. 49-57)
14 Mar 1968 SANTA CRUZ lost to COCHISE when the boundary was redefined to run
along the east line of range 18 east. (Ariz. Laws 1968, 28th leg., 1st reg.
sess., ch. 82/ pp. 180-182)
09 Jan 1852 SOCORRO (N.M.) created by New Mexico Territory from non-county area;
included parts of present Arizona and New Mexico. (N.M. Terr. Laws 1851, 1st
assy., 1st sess./p. 119; N.M. Terr. Laws 1851, 1st assy., 2d sess. /pp. 266,
292)
24 Feb 1863 SOCORRO (N.M.) eliminated from Arizona when Arizona Territory was
created from the western portion of New Mexico Territory. (U.S. Stat., vol. 12,
ch. 56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van
Zandt, 162)
22 Sep 1846 TAOS (N.M.) established as one of seven original New Mexico counties under
Kearny's Code of Laws for the occupied Mexican territory; located entirely in
New Mexico [not mapped]. (Kearny's Code 1846, "Courts and Judicial
Powers", secs. 5-7/p. 49; Abel, Map #2; Coan, 252; Williams, 108-109)
09 Jan 1852 TAOS (N.M.) gained from non-county area, and exchanged with RIO ARRIBA
(N.M.) and SAN MIGUEL (N.M.) when all counties redefined; included parts of
present Arizona, Colorado, Nevada and New Mexico. (N.M. Terr. Laws 1851,
1st assy., 2d sess. /p. 291)
01 Feb 1860 TAOS (N.M.) lost to creation of MORA (N.M.); the part of TAOS in present
Arizona was unchanged. (N.M. Terr. Laws 1859-1860, 9th assy. /p.
76)
12 Jan 1861 TAOS (N.M.) lost to creation of SAN JUAN (N.M. Territory, original, extinct).
(N.M. Terr. Laws 1860-1861, 10th assy. /p. 16)
28 Feb 1861 TAOS (N.M.) lost to creation of Colorado Territory; the part of TAOS in present
Arizona was unchanged. (U.S. Stat., vol. 12, pp. 172-177; Van Zandt,
141-144)
18 Jan 1862 TAOS (N.M.) gained all of SAN JUAN (N.M. Territory, original, extinct); SAN
JUAN eliminated. (N.M. Terr. Laws 1861-1862, 11th assy. /p. 16)
24 Feb 1863 TAOS (N.M.) eliminated from Arizona when Arizona Territory was created from
the western portion of New Mexico Territory. (U.S. Stat., vol. 12, ch.
56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van
Zandt, 162)
04 Jul 1848 Treaty of Guadalupe-Hidalgo ended the war between Mexico and the United
States. Area ceded by Mexico became Unorganized Federal Territory (non-
county area) in the United States; included all of present California, Nevada,
and Utah, and parts of present Arizona, Colorado, New Mexico, and
Wyoming. Part of the international boundary was in dispute. Map shows only
the part Unorganized Federal Territory in present Arizona. (U.S. Stat., vol. 9,
pp. 922-943; Parry, 102: 29-59; Van Zandt, 11, 28-29; Walker and Bufkin, 19,
20A)
13 Dec 1850 The United States created New Mexico Territory from Unorganized Federal
Territory and land purchased from the state of Texas; all that portion of
Unorganized Federal Territory lying outside the boundaries of the seven
original counties established under Kearny's Code became non-county area in
New Mexico Territory. (U.S. Stat., vol. 9, ch. 49[1850]/pp. 446-452; Baldwin,
117-137; Coffey, 145-164; Van Zandt, 28-29, 162-165)
22 Sep 1846 VALENCIA (N.M.) established as one of seven original New Mexico counties
under Kearny's Code of Laws for the occupied Mexican territory; located
entirely in New Mexico [not mapped]. (Kearny's Code 1846, "Courts and
Judicial Powers", secs. 5-7/p. 49; Abel, Map #2; Coan, 252; Williams, 108-109)
09 Jan 1852 VALENCIA (N.M.) gained from non-county area, lost to creation of SOCORRO
(N.M.), and lost to BERNALILLO (N.M.) when all counties redefined; included
parts of present Arizona, Nevada, and New Mexico. (N.M. Terr. Laws 1851,
1st assy., 2d sess. /p. 292)
24 Feb 1863 VALENCIA (N.M.) eliminated from Arizona when Arizona Territory was created
from the western portion of New Mexico Territory. (U.S. Stat., vol. 12, ch.
56[1863]/pp. 664-665; Ariz. Terr. Laws 1864, 1st assy./ pp. vii-viii; Van Zandt,
162)
10 Nov 1864 YAVAPAI created as one of four original counties in Arizona Territory. (Howell
Code, Ariz. Terr. Laws 1864, 1st assy., ch. 2/ pp. 24-25)
14 Feb 1871 YAVAPAI lost to creation of MARICOPA. (Ariz. Terr. Laws 1871, 6th assy./ pp.
53-54)
31 Jan 1877 YAVAPAI lost to MARICOPA. (Ariz. Terr. Laws 1877, 9th assy./ pp. 12-13)
14 Feb 1879 YAVAPAI lost to creation of APACHE. (Ariz. Terr. Laws 1879, 10th assy./ pp.
96-97)
06 Mar 1883 YAVAPAI exchanged with MOHAVE. (Ariz. Terr. Laws 1883, 12th assy./ p.
171)
21 Mar 1889 YAVAPAI lost to GILA. (Ariz. Terr. Laws 1889, 15th assy./ pp. 49-52)
19 Feb 1891 YAVAPAI lost to creation of COCONINO. (Ariz. Terr. Laws 1891, 16th assy./
pp. 26-34)
19 Mar 1891 YAVAPAI lost to GILA. (Ariz. Terr. Laws 1891, 16th assy./ pp. 102-103)
10 Nov 1864 YUMA created as one of four original counties in Arizona Territory. (Howell
Code, Ariz. Terr. Laws 1864, 1st assy., ch. 2/ pp. 24-25)
02 Apr 1963 YUMA boundary with the state of California was redefined as part of an
interstate compact to account for changes in the course of the Colorado River
[not mapped]. (Ariz. Laws 1963, 25th leg., 1st reg. sess., ch. 77/ pp. 142-150)
27 Apr 1983 YUMA lost to creation of LA PAZ. (Ariz. Laws 1983, 36th assy., ch. 291/pp.
1089-1094)
