Alta California Alta California (Spanish) Province in the Viceroyalty of New Spain Territory and department in independent Mexico ← 1804–1848 → Location of California, Alta Map of independent Mexico before 1848, with Alta California in red, showing the northern border established in 1819 by the Adams-Onis Treaty Capital Monterey 36°36′N 121°54′W﻿ / ﻿36.600°N 121.900°W﻿ / 36.600; -121.900Coordinates: 36°36′N 121°54′W﻿ / ﻿36.600°N 121.900°W﻿ / 36.600; -121.900 Governor (See also complete list) • 1804–14 José Joaquín de Arrillaga (first Spanish governor) • 1815–22 Pablo Vicente de Solá (last Spanish governor) • 1822–25 Luis Antonio Argüello (first Mexican governor) • 1845–46 Pío de Jesus Pico IV (last Mexican governor) Historical era Spanish colonization of the Americas • Las Californias 1769 • Las Californias split into Alta and Baja 1804 • Mexican independence August 24, 1821 • Mexican-American War May 13, 1846 • Mexican Cession by treaty February 2, 1848 • California statehood September 9, 1850 Population • 1847 85,000[1] Today part of United States - California - Arizona - Nevada - Utah - Colorado - Wyoming