Riverside County, California: History
=== Indigenous ===
The Indigenous peoples of the valleys, mountains and deserts of what is now Riverside County are the Serrano, the Payómkawichum, the Mohave, the Cupeno, the Chemehuevi, the Cahuilla, and the Tongva. The Aguanga and Temecula Basins, Elsinore Trough and eastern Santa Ana Mountains are the traditional homelands of the Payómkawichum. The inland valleys in the Santa Rosa and San Jacinto Mountains and the desert of the Salton Sink are the traditional homelands of the Cahuilla.
The first European settlement in the county was a Mission San Luis Rey de Francia estancia or farm at the Luiseño village of Temescal. In 1819, the Mission granted Leandro Serrano permission to occupy the land for the purpose of grazing and farming, and Serrano established Rancho Temescal. Serrano was mayordomo of San Antonio de Pala Asistencia for the Mission of San Luis Rey.
With the signing of the Treaty of Cordoba in 1821, Mexico gained its independence from Spain, but the San Gabriel Mission near what is now Los Angeles, California, continued to expand, and established Rancho San Gorgonio in 1824. The ranch was to be one of the Mission's principal rancherias, and the most distant, and it occupied most of today's San Gorgonio Pass area.
Following the Mexican secularization act of 1833 by the First Mexican Republic, a series of rancho land grants were made throughout the state. In the Riverside County this included; Rancho Jurupa in 1838, El Rincon in 1839, Rancho San Jacinto Viejo in 1842, Rancho San Jacinto y San Gorgonio in 1843, Ranchos La Laguna, Pauba, Temecula in 1844, Ranchos Little Temecula, Potreros de San Juan Capistrano in 1845, Ranchos San Jacinto Sobrante, La Sierra (Sepulveda), La Sierra (Yorba), Santa Rosa and San Jacinto Nuevo y Potrero in 1846.
New Mexican colonists founded the town of La Placita on the east side of the Santa Ana River at the northern extremity of what is now the city of Riverside in 1843.
When the initial 27 California counties were established in 1850, the area today known as Riverside County was partially in Los Angeles County and partially in San Diego County. In 1853, the eastern part of Los Angeles County was used to create San Bernardino County. Between 1891 and 1893, several proposals and legislative attempts were put forth to form new counties in Southern California. These proposals included one for a Pomona County and one for a San Jacinto County. None of the proposals were adopted until a measure to create Riverside County was signed by Governor Henry H. Markham on March 11, 1893.
The new county was created from parts of San Bernardino County and San Diego County. On May 2, 1893, seventy percent of voters approved the formation of Riverside County. Voters chose the city of Riverside as the county seat, also by a large margin. Riverside County was officially formed on May 9, 1893, when the Board of Commissioners filed the final canvass of the votes. …