Vacaville is a city located in Solano County in Northern California. Sitting approximately 35 miles (56 km) from Sacramento and 55 miles (89 km) from San Francisco, it is part of the San Francisco Bay Area but also considered, at least by some agencies, to be part of the Sacramento Valley. As of the 2017, Vacaville had a population of 100,328, making it the third largest city in Solano County.