Petaluma is a city in Sonoma County, California, in the United States. Its population was 57,941 according to the 2010 Census. The Rancho Petaluma Adobe, located in Petaluma, is a National Historic Landmark. Its construction started in 1836 by order of General Mariano Guadalupe Vallejo, then Commandant of the San Francisco Presidio. It was the center of a 66,000 acre (270-km²) ranch stretching from Petaluma River to Sonoma Creek.