Sullivan County is named for James Sullivan, who was a general during the American Revolutionary War.
Surrounding County Courthouses:
N – Putnam County
E – Putnam County and Adair County
S – Linn County
W – Grundy County and Mercer County
Created: February 14, 1845 
County Seat:
Milan 1845 – present
County Courthouse – Milan
Location: 109 North Main Street / East 3rd Street
Built: 1938 – 1939
Style: Art Deco
Architect: Lyle V DeWitt
Contractor: Walter Barenfanger of Vandalia, Illinois.
Description: The building faces south and is a three story Indiana buff colored limestone and concrete structure. The rectangular shaped building is located on landscaped grounds in the center of Milan. The building is 110 feet by 66 feet and has a projecting center section with recessed windows and entrance which rises above the roof line. The roof line is flat with a limestone cornice. In the interior, the County Circuit Court courtroom is located on the second story. The building houses the County Circuit Court of the 9th Judicial Circuit.
See: The 9th Judicial Circuit includes Chariton County, Linn County and Sullivan County.
History: The county was created in 1845 as Highland County and Milan was selected as the county seat. The first courts met at the residence of Armstead C Hill in May 1845. The first courthouse was built by William Putnam in 1847 at a cost of $300. The second courthouse was constructed by Major John McCullough in 1857 to 1858 at a cost of $5,000. Fire destroyed the building on June 26, 1908 and the county purchased a two-story, brick building erected by the O K Railroad Company at a cost of $6,000. The third and present courthouse was constructed in 1938 to 1939.
County Courthouse – Milan
Photos taken 2009