Middletown is a census-designated place in Lake County, California, United States. The population was 1,020 at the 2000 census. Middletown was given its name because it is halfway between Lower Lake to the North and Calistoga to the South. Middletown apartments for rent comparison page shows most up to date rent information on Middletown apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.