While the American and French Revolutions were changing the political and social shape of Europe, the Spanish were altering forever the fortunes of the then current California residents. In the 1740s, Russian trappers had moved across the Bering Straight and begun what was to be the near decimation of the sea otter population in the northern Pacific. Although a permanent Russian settlement in California must wait until 1812, the Spanish thought it necessary in the late 1760s to move northward from Baja California to establish outposts in Monterey and what was to become San Francisco.

During the 54 years following the founding of the first mission at San Diego, 21 missions appeared, more than half in the first 20 years. Many have been engulfed by urban growth, leaving only La Purisima, San Miguel and San Antonio in their natural setting.