It is in the Eastern Standard time zone. Elevation is 620 feet. More than 310 years ago the area that is now Watertown belonged to the local Paugasuck Indians. But in 1684, Thomas Judd and 35 other proprietors bought the land from the Indians and Town history began. Watertown is a town in Litchfield County, Connecticut, United States. The population was 21,661 at the 2000 census. The zip code for Watertown is 06795. It is a suburb of Waterbury. It borders the towns of Woodbury, Middlebury, Litchfield, Plymouth, Bethlehem, and Thomaston.