Jefferson County is named for Thomas Jefferson, who was President of the United States from 1801 to 1809.
Surrounding County Courthouses:
N – Ontario, Canada and Saint Lawrence County
E – Lewis County
S – Oswego County
W – Lake Ontario and Ontario, Canada
Created: March 28, 1805 
County Seat:
Watertown 1805 – present
Old County Courthouse – Watertown
Location: 195 Arsenal Street / Sherman Street
Built: 1862 – 1863
Style: Romanesque
Architect: Horatio Nelson White of Syracuse
Contractor: John Hose of Herkimer and David Kieff.
Description: The building faces north and is a two story red brick and limestone trimmed structure. The building is located on landscaped grounds in the center of Watertown. The building is square and set on high foundations. The north front has a projecting triple arched entrance with three arched windows on the second story. The northwest corner has a square red brick tower. The second story courtroom is now the Board of Legislators Chamber. There are horizontal cornices above the first story and along the roof line.
See: National Register of Historic Places – Old Jefferson County Courthouse
County Courthouse – Watertown
Location: 163 Arsenal Street / Arcade Street
Built: 1999 – 2000
Style: Modern
Architect: Unknown
Contractor: Unknown
Description: The building faces north and is a four story glass, limestone and concrete structure. The building is located on landscaped grounds in the center of Watertown. The central section is a glass wall rising from the entrance to the flat roof line. Glass walls rise on the first and second stories of the east section. The west section is the old Post Office which has stone work on the first story and an overhanging eave at the flat roof line.
History: The county was created in 1805 and Watertown was selected as the county seat. The first courthouse was a two story structure on Coffeen Street built in 1807 to 1808 at a cost of $5,100. The courthouse was damaged by fire in 1817, was patched up and finally destroyed by fire in 121. The second courthouse was built in 1821. The third courthouse was constructed in 1862 to 1863 and is still standing. The fourth and present courthouse was constructed in 1999 to 2000.
See: The 5th Judicial District includes Herkimer County, Lewis County, Oneida County, Onondaga County and Oswego County.
County Administration Building – Watertown
Location: 175 Arsenal Street / Sherman Street
Built: 1963 – 1964
Style: Modern
Architect: Parker-Soper
Contractor: A Frederick & Sons
Description: The building faces north and is a seven story concrete and glass structure. The building is located on landscaped grounds in the center of Watertown. The roof line is flat. The building was expanded in 1974 to 1975. The architect was Parker-Soper and the contractor was Perfetto & Whaler Construction Corporation.
County Clerk’s Office – Watertown
Location: 163 Arsenal Street / Sherman Street
Built: 1883 – 1884
Style: Georgian
Architect: Unknown
Contractor: Unknown
Description: The building faces west and is a two story red colored brick style structure. The building is located on landscaped grounds in the center of Watertown. The building is rectangular. Additions were made in 1933 and 1953.
Old County Courthouse – Watertown
County Courthouse – Watertown
County Administration Building – Watertown
Photos taken 2010