Watertown is a city in Dodge and Jefferson counties in the U.S. state of Wisconsin. Most of the city's population is in Jefferson County. Division Street, several blocks north of downtown, marks the county line. The population of Watertown was 22,926 at the 2020 census. Of this, 14,674 were in Jefferson County, and 8,252 were in Dodge County. Watertown is the largest city in the Watertown-Fort Atkinson micropolitan area, which also includes Johnson Creek and Jefferson.

Dodge County is a county located in the U.S. state of Wisconsin. As of the 2020 census, the population was 89,396. Its county seat is Juneau. The county was created from the Wisconsin Territory in 1836 and organized in 1844.