which county is vacaville, ca in
Homefacts City Report. Vacaville is located in Solano County, CA. The population is 93,899, making Vacaville the 3rd largest city in Solano County. There are 19 public schools in Vacaville with an average Homefacts rating of B. The total crime rate for Vacaville is very low, and there are 100 registered sex offenders residing in the city.