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A Century of

California Post Offices









Twenty-one LISTS


Official and Unofficial of

Post Offices Established in the Period

1848 to 1859












Counties Created in 1850





The original twenty-seven counties were created and described by Act of the Legislature approved by the Governor 18 February 1850:


Branciforte-Name was changed to Santa Cruz in March, 1850 Statutes 1850: 155-6


Butte-Lost Plumas 1854, including portion of present Lassen; and portion of Tehama in 1856, with further adjustment in 1859. The southern (Sutter) boundary was shifted in 1851, 1852, 1854, 1856; and was redefined in 1864 to conform to section lines. The area between Sacramento River and Butte Creek was lost to Colusa in 1856, modified in 1872. The Butte-Yuba line was changed in 1860, placing Strawberry Valley in Yuba; and in 1861, placing Woodville House in Yuba. Minor adjustments were made in 1872, 1874, 1897, 1901, 1915 and 1923, generally to place the boundaries on official land survey lines.


Calaveras- Originally a large county, Amador was created from its northern part in 1854; Mono took all east of the Sierra in 1861; Alpine a small portion in 1864.


Colusa-(Colusi until 1857) Has been completely changed from its original area except a six-mile strip along its present northern boundary. “All that part of Tehama south and west of Red Bluff and the whole of Glenn County were at one time included within the bounds of Colusa, while on the other hand, the greater part of present Colusa was originally within Yolo County.”

1851. Northern boundary was moved slightly south, yielding area to Shasta; the southern (Yolo) boundary was moved southerly to approximately its present position.

1856. Creation of Tehama took about one-fourth of Colusa; but the boundary was not defined until 1872, when established approximately along the northern line of present Glenn County. The eastern boundary was shifted from Sacramento River easterly to Butte Creek, taking area from Butte.

1868.Western (Mendocino) boundary was defined.

1891.Glenn County was detached, including the town of Princeton and surrounding area which were returned to Colusa in 1893.


*Briefed from “California County Boundaries, A Study of the Division of the State into Counties and the Subsequent Changes in Their Boundaries”, by Owen C. Coy, Ph.D., published by the California Historical Survey Commission, Berkeley, 1923.


Contra Costa- The San Joaquin line was adjusted in 1851. The southern portion went to Alameda in 1853.


El Dorado- Lost a small southern portion between Dry Creek and Cosumnes River to Amador in 1855 and 1857, and a small south-eastern area to Alpine in 1864. Eastern portion of the northern (Placer) boundary was adjusted in 1863.


Los Angeles- Was greatly expanded in 1851, becoming one of the largest counties in the State by receiving portions of San Diego and Mariposa counties; but San Bernardino was detached in 1853. In 1866 Kern acquired the portion north of the present Los Angeles-Kern line. Orange was detached in 1889.


Marin- The area remains substantially unchanged. Angel Island and certain Bay areas were acquired from San Francisco in 1860.


Mariposa- Was originally one of the largest counties, including present Mariposa, Merced, Madera, Fresno, Kings and Tulare, plus large parts of Kern, Mono, and Inyo.

1852. Lost Tulare County, which then included all of the present Kings, and parts of Kern, Fresno, Mono and Inyo.

1855. Lost Merced, which then included part of present Fresno and Madera.

1856. Lost most of Fresno, including part of present Madera.


Mendocino- Was named and described in 1850, but was attached to Sonoma for administration until 1859. Originally it included much of present Lake, and all of Sonoma north and west of Russian River. The Napa line was changed in 1852 and 1855, giving Napa the Clear Lake drainage. In 1855 the Sonoma boundary was moved far west of Russian River, and in 1859 the present Mendocino-Sonoma line was established approximately. In 1864 a district north of Clear Lake drained by Eel River was surrendered to Glenn in 1907. In 1917 slight changes were made in the Lake and Sonoma boundaries.


Monterey- Was extended southerly by taking from San Luis Obispo in 1851; lost San Benito in 1874; other boundary adjustments have been minor.


Napa- The original boundaries were very uncertain excepting in the southern area, and were better defined in 1852. Changes in 1852 and 1855 gave Napa the entire Clear Lake drainage area. In 1855 the southern boundary was changed to approximately its present lines. Lake was detached in 1861, and boundaries modified slightly in 1864 and 1868. Knox Township was transferred from Lake to Napa in 1872.


Sacramento- No important changes. A small delta of the Mokelumne was surrendered to San Joaquin in 1870.


San Diego- At first included practically all of present San Diego, Imperial, Riverside and San Bernardino. In 1851 it surrendered area to Los Angeles which afterwards became San Bernardino; lost most of Riverside in 1893, and all of Imperial in 1907.


San Francisco- Lost Angel Island and upper San Francisco Bay in 1854; regained the upper Bay in 1857, but lost it again in 1860; lost San Mateo in 1856; other boundary changes have been minor.


San Joaquin- The Contra Costa line was adjusted in 1851. The south-eastern triangle, north of Stanislaus River, went to Stanislaus in 1860 (including Knights Ferry).


San Luis Obispo- No important changes; lost small area to Monterey in 1851; Rancho Santa Maria was alternately in San Luis Obispo and Santa Barbara until 1872, when present line was defined.


Santa Barbara- No major changes except Ventura was detached in 1872; the southeastern boundary (Los Angeles) was redefined in 1851, 52, 54.


Santa Clara- No important changes except loss of Washington Township to Alameda in 1853.


Santa Cruz- (Originally Branciforte) Northern portion was lost to San Mateo in 1868.


Shasta- South (Tehama) boundary was moved south in 1851 and north in 1856; was again adjusted in 1857. The northern half was detached in 1852 to become the greater part of Siskiyou; the eastern half of the remainder, supplemented by Plumas area, became Lassen in 1864.


Solano- Mare Island was acquired from Sonoma in 1853; Napa boundary was adjusted in 1855; Yolo boundary in 1857.


Sonoma- Mare Island was excluded in 1853; Napa and Marin lines were adjusted in 1855. The Mendocino line was changed radically in 1855 and 1859, adding to Sonoma a large area west and north of Russian River.


Sutter- Lost one-third of area to Placer in 1851, line adjusted in 1866; northern boundary was moved south in 1851, but substantially restored in 1856.


Trinity- Originally included all of present Trinity, Humboldt, Del Norte and much of Siskiyou, and was attached to Shasta for administration. It was organized in 1851 and surrendered northern half to Klamath same year. Humboldt was detached in 1853. Received headwaters of Trinity River from Klamath in 1855.


Tuolumne- Western (Valley) portion became Stanislaus in 1854; a small area east of the Sierra was lost to Alpine 1864.


Yolo- (Originally Yola) Lost north half to Colusi (Colusa) in 1851; Solano boundary was adjusted in 1857.


Yuba- Lost approximately one-half its area to Placer and Nevada in 1851; Sierra was detached in 1852. The Yuba-Butte line was adjusted in 1860, fixing Strawberry Valley and Woodville House in Yuba; this boundary was further adjusted in 1897 to conform to land survey lines. In 1866 Yuba yielded to Sierra a small area lying northeast of North Yuba River and Canon Creek.


Counties Created After 1850


Klamath- Created 25 April 1851, dissolved 28 March 1874. Originally it consisted of all State area lying west of the summit of the Coast range, north of a line drawn easterly through the mouth of Mad River. In 1852 Skskiyou took the eastern part; the southern part was attached to Trinity in 1855; and Del Norte was detached in 1857. In 1875, the remainder of Klamath was divided between Humboldt and Siskiyou.


Nevada- Created 25 April 1851 from the southern and eastern parts of Yuba. In 1852 a strip from Yuba was added along the northern boundary; in 1856 the line was moved still farther north to the middle fork of the Yuba River at the expense of Sierra County, which had been created in the meantime.


Placer- Created from Yuba and Sutter area. In 1863 a small area near Lake Tahoe was gained from El Dorado, lost in 1913. In 1866 a small western portion was returned to Sutter. In 1913 some 800 square miles south of Rubicon River was gained from El Dorado when the boundary was adjusted to land survey lines.




Sierra- Created from the eastern portion of Yuba. In 1856 a small southern area was surrendered to Nevada County. In 1863 a narrow strip along the northern boundary was acquired from Plumas.


Siskiyou- Created from the northern part of Shasta and the eastern part of Klamath. In 1874 Modoc was detached; but in 1875 Siskiyou acquired approximately half of Klamath. The Del Norte boundary was adjusted in 1887 to give Happy Camp and adjacent area along Klamath River to Siskiyou; and in 1901 was adjusted to section lines.


Tulare- Created from the southeastern half of Mariposa. A small area was lost to Fresno in 1856. Inyo and Kern were detached in 1866; Kings in 1893. The Tulare-Fresno line was adjusted in 1874 and 1876. Other changes have been essentially adjustment and definition of lines.




Alameda- Created 25 March 1853 from portions of Contra Costa and Santa Clara. The original boundaries remain substantially unchanged.


Humboldt- Created 12 March 1853 from Trinity area. It received approximately half of Klamath in 1875. The Del Norte boundary was adjusted to land lines in 1901.


San Bernardino- Created 26 April 1853 from the eastern portion of Los Angeles County. It lost its northern portion to Inyo in 1872; and its southern portion, including important southwestern area, to Riverside in 1893. The western boundary (Kern) was adjusted several times before being quite definitely fixed in 1878; but another dispute was not settled until 1917.




Amador- Created 10 May 1854 from that portion of Calaveras lying north of the Mokelumne River. In 1855 and 1857, El Dorado area between Dry Creek and the Cosumne River was added; and El Dorado yielded a small eastern area in 1863. Creation of Alpine in 1864 took the eastern third of Amador.


Plumas- Created from Butte area. The southern (Sierra) boundary was adjusted in 1863, 1866 and 1868. The northeastern portion, including Honey Lake and Susanville, went into Lassen in 1864. In 1901 the Butte and Lassen boundaries were adjusted to land survey lines.


Stanislaus- Created 5 April 1854 from Tuolumne area. In 1860 a triangle north of Stanislaus River, including Knights Ferry, was added from San Joaquin County. Temporarily, 1866 to 1868, a substantial portion of Merced County was attached to Stanislaus.




Merced- Created 19 April 1855 from Mariposa County. It lost heavily to Fresno in 1856, and temporarily, 1866 to 1868, lost to Stanislaus. Otherwise, the present boundaries coincide closely with the original.




Fresno- Created 19 April 1856 from the southeastern parts of Merced and Mariposa, and a small portion of Tulare. The portion east of the Sierra Nevada was taken by Mono in 1861; present Madera was detached in 1893. The Fresno-Tulare line was adjusted in 1874 and 1876; the San Benito line was adjusted in 1887 and the Kings line in 1909, all with some loss to Fresno.


San Mateo- Created from the southern part of San Francisco. The original boundaries remain almost unchanged except a substantial area was annexed from Santa Cruz in 1868.


Tehama- Created from Colusa, Butte and Shasta areas. A substantial area was added from Butte in 1857, the boundary being re-defined in 1859.




Del Norte- Created 2 March 1857 from Klamath area. No important changes were made until 1887, when a large northeastern area was surrendered to Siskiyou; also, Happy Camp and adjacent Klamath River area. Del Norte recovered a small portion of this loss in 1901.




Lake- Created from Napa area. Additions were made to the north in 1864 from Mendocino and to the east in 1867 from Colusa. Knox Township in Putah Valley was lost to Napa in 1872. The boundary with Mendocino was more precisely defined in 1907 and 1917, and with Glenn in 1909.


Mono- Created from Calaveras and Fresno. It lost a small northern area to Alpine in 1864; and a large southern area to Inyo in 1866 and 1870.




Alpine- Created 16 March 1864 from El Dorado, Amador, Calaveras and Tuolumne areas. There have been no significant changes.


Lassen- Created 1 April 1864 from Plumas and Shasta area. Changes have been minor.




Inyo- Created 22 March 1866 from Tulare and Mono area. In 1870 the boundary was moved to the north by taking from Mono; in 1872 to the south at the expense of San Bernardino and Kern.


Kern- Created from portions of Tulare and Los Angeles. Changes have been limited to defining boundaries, particularly the eastern (San Bernardino) line in 1878 and 1917.




Ventura- Created from the eastern portion of Santa Barbara County. The boundaries remain substantially unchanged, except for a survey in 1881 of the eastern boundary, which added approximately 275 square miles from Los Angeles County.




Modoc- Created 17 February 1874 from the eastern portion of Siskiyou County. There have been no changes since.


San Benito- Created 12 February 1874 from the portion of Monterey County east and north of the Gabilan Mountains. In 1887 the eastern boundary was moved easterly at the expense of Fresno and Merced.




Orange- Created 11 March from Los Angeles area. The lines remain unchanged.




Glenn- Created 11 March 1891 from Colusa area. The town of Princeton and surrounding area was included, but was returned to Colusa in 1893. Glenn was enlarged somewhat by placing the Mendocino boundary on land survey lines in 1907, and the Lake County boundary in 1909.




Kings- Created 22 March 1893 from Tulare area. In 1909 a triangle north of Lemoore was added from Fresno.


Madera- Created 11 March 1893 from Fresno area. The original lines remain unchanged.


Riverside- Created 11 March 1893, took 6,044 square miles from San Diego and 590 miles from San Bernardino. The lines were more precisely defined in 1919, but without substantial change.




Imperial- Created 15 August 1907 from the eastern half of San Diego. The original boundaries remain unchanged.






Transcribed by: Jeanne Sturgis Taylor.

Source: Frickstad, Walter N.,  A Century of California Post Offices 1848-1954, Pages 365-371. Philatelic Research Society, Oakland, CA. 1955.

© 2012  Jeanne Sturgis Taylor.


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