Los Angeles County's original boundaries, when California first became a state, included present-day Orange County and portions of present-day Ventura and Riverside Counties.
Map showing Los Angeles County, 1850 (dotted box added to image). From California County Boundaries by Owen C. Coy & California Historical Survey Commission, 1923.
For a brief time, Los Angeles County's boundaries were considerably extended to absorb portions of neighboring Mariposa and San Diego Counties. It created the largest extent of the county, reaching as far as California's current state line with neighboring Nevada and Arizona. Then, Los Angeles County included all of the present-day counties of Orange and San Bernardino and portions of present-day Ventura, Riverside, and Kern Counties.
Map showing Los Angeles County, 1852 (dotted box added to image). From California County Boundaries by Owen C. Coy & California Historical Survey Commission, 1923.
A year after Los Angeles County's greatest expansion, extending all the way to the state line with present-day Nevada and Arizona, the eastern portion of the couty was split off to form newly-established San Bernardino County. Los Angeles County continued to include all of present-day Orange County and portions of present-day Ventura and Kern Counties.
Map showing Los Angeles County, 1860 (dotted box added to image). From California County Boundaries by Owen C. Coy & California Historical Survey Commission, 1923.
Los Angeles County's boundaries contracted further after its northern portion broke off to become part of newly-established Kern County.
Map showing Los Angeles County, 1867. Map by Leander Ransom, A.J. Doolittle, George H. Baker, Warren Holt, courtesy Library of Congress.
After a portion was carved out to became part of newly-established Ventura County in 1873, Los Angeles County was reduced to almost all of what is now its present-day territory and all of what is present-day Orange County.
Map of Los Angeles County, 1888. Map by V.J. Rowan & Schmidt Label & Litho. Co., courtesy Library of Congress.
Los Angeles County was further reduced in size when its southern portion split off to establish the new Orange County.
Map of Los Angeles County, 1898. Map by E.T. Wright, C.N. Perry & Los Angeles Lithographic Co., courtesy of Library of Congress.
Since 1889, only very small adjustments were made to Los Angeles County's boundaries. The most recent was in 2001 when a small portion of northwestern Los Angeles County was transferred over to Kern County, so that residents there could be more conveniently served by that county. In 2005, residents of the neighboring Los Angeles County unincorporated community of Gorman also sought approval to transfer over to Kern County. Their efforts, however, were not successful.
Before and after maps showing a small portion of Los Angeles County transferred to Kern County. Los Angeles Almanac Maps.
