People of African descent have been part of California since Spanish colonization in the eighteenth century. Many of those residents flourished after Mexico (which included California) became independent from Spain in 1821. Their lives changed dramatically, however, when the US took control of California following the Mexican-American War of the 1840s.
Pío Pico, the last governor of Mexican California, was like many Californians of his day insofar as he was of mixed African, Native, and Spanish ancestry. In contrast, the first governor of the US state of California, Peter Burnett, was a former Southern slaveholder who joined other white Californians in attempting to exclude Black people from the state. Although that effort proved unsuccessful, Black Californians soon faced a wide range of restrictions - many of which they successfully combated through initiatives like the statewide Conventions of Colored Citizens.
Upon his return to California McDonald hoped to enlist in the Marines. When he learned that the Marines only accepted white recruits, he changed his plans and went to work aboard the Sacramento River steamboat Modoc. Beginning with his work on the Sacramento River, many of McDonald’s earliest personal and career relationships were with immigrants from Denmark, Italy, Sweden, Ireland, and elsewhere.
McDonald soon left life on the river and settled in the town of Mayfield (now part of Palo Alto). There he began working on a Page Mill Road ranch that belonged to local saloon-owner and former sailor Fred Behm. Within a year McDonald was managing the Behm’s ranch.
During his time at the ranch McDonald began correspondence courses in law and meteorology. This afforded him a means of pursuing an education that he continued for many years.