Formed January 2, 1818 (15th county)
Washington County (13,767), Nashville (3,100)
A red brick courthouse, built in 1884 and enlarged in 1965, sits on St. Louis Street between Northeast and Northwest Court streets. Illinois State Highway 15 is St. Louis Street in the town. John Seyler designed this Italianate and Second Empire style courthouse. The courthouse sits on a hill with veteran memorials on the grounds. Washington County was formed from Saint Clair County on January 2, 1818 as the 15th county with Covington as the first county seat followed by Georgetown in 1827. Nashville assumed the county seat in 1831. The county is named for President George Washington. The county seat is named for Nashville, Tennessee.
Washington County government consists of a sheriff, an attorney, a coroner, a clerk, a treasurer, and an assessor (executive). It has 15 Board Members (legislative.) Twenty-four Circuit Court Judges serve Washington, Monroe, Perry, Randolph, and St. Clair counties and a court clerk serves Washington County (judicial.) Washington County is located in south central Illinois. Saint Louis, Missouri is west and Evansville, Indiana is southeast of the county. The Kaskaskia River forms its northwest border. The county center is 4.9 miles Northwest of Nashville. The county is surrounded clockwise by Clinton, Marion, Jefferson, Perry, Randolph, and Saint Clair counties.
The area of the county is 562 square miles. It is 44 out of 102 in the state. It ranks 77 out of 102 in population in the state. It has a density of 24.5 persons per square mile making it 84 out of 102 in the state. Washington County has 54.6% of its population in its incorporated areas. Interstate Highway 64 crosses from east to northwest in the county from Jefferson County to Clinton County. United States Highway 51 travels north to south through the eastern part of the county from Marion County to Perry County. The county looks like a rectangle with its northwest corner pushed in. Nashville is slightly east and south of center in the county. Nashville is the county seat and the largest city. It is 22.5% of the county population.
Addieville
Ashley
Du Bois
Hoyleton
Irvington
Nashville
New Minden
Oakdale
Okawville
Radom
Richview
Venedy
Centralia
Wamac