William Alexander Leidesdorff, Jr. (October 23, 1810 – May 18, 1848) was one of the earliest biracial-black U.S. citizens in California and one of the founders of the city that became San Francisco. A highly successful, enterprising businessman, he was a West Indian immigrant of African Cuban, possibly Carib, Danish/Swedish and Jewish ancestry. Leidesdorff became a United States citizen in New Orleans in 1834. He migrated to Alta California in 1841, then under Mexican rule, settling in Yerba Buena (now San Francisco), a village of about 30 Mexican and European families.