Antonio Maria Osio's La Historia de Alta California was the first written history of upper California during the era of Mexican rule, and this is its first complete English translation. A Mexican-Californian, government official, and the landowner of Angel Island and Point Reyes, Osio writes colorfully of life in old Monterey, Los Angeles, and San Francisco, and he gives a first-hand account of the political intrigues of the 1830s that led to the appointment of Juan Bautista Alvarado as governor.

Osio wrote his History in 1851, conveying with immediacy and detail the years of the U.S.-Mexican War of 1846-1848 and the social upheaval that followed. As he witnesses California's territorial transition from Mexico to the United States, he recalls with pride the achievements of Mexican California in earlier decades and writes critically of the onset of American influence and imperialism.

Unable to endure life as foreigners in their home of twenty-seven years, Osio and his family left Alta California for Mexico in 1852.