Jefferson County Courthouse Complex is a courthouse complex and national historic district located at Watertown in Jefferson County, New York. The district includes three contributing buildings; the courthouse building (1862), Clerk's Office (1883–1884) and Surrogate's Office (1905). The courthouse building is a two story, red brick structure with limestone trim. It features a three story tower on the northwest corner. It was designed by noted architect Horatio Nelson White. It was listed on the National Register of Historic Places in 1974.