The chain of twenty one Spanish Franciscan missions Junipero Serra and his successors built along the California coast between 1769 and 1823 was, on the church's own terms, an evangelizing project, and modern scholarship on Serra has been explicit that the conversions it produced relied heavily on coercion, forced labor and a mission system that devastated Indigenous populations through disease and disruption of traditional life, a history the state and the church have both had to reckon with directly in recent decades rather than treat as settled. The missions nonetheless remain the oldest continuous thread of organized religion in the state and shaped its earliest colonial geography from San Diego to Sonoma.
A century later California became the source of a very different kind of religious history. The Azusa Street Revival, beginning in 1906 in a converted livery stable in Los Angeles under the leadership of William Seymour, a Black preacher and the son of formerly enslaved parents, is treated by historians of the movement as the founding event of modern global Pentecostalism, a tradition that by the early twenty first century had grown into one of the largest branches of Christianity worldwide. The revival's own interracial worship, unusual for the period, was itself part of what participants and later scholars read as evidence of the Spirit at work. California kept producing new religious movements after Azusa Street as well, from the Vedanta Society's early Hindu missionary presence to Zen centers and the human potential movement, an unusually high concentration of religious innovation for one state across three centuries.