Jefferson

Formed December 17, 1818 (10^th county)

Jefferson County (226,572), Hillsboro (3,474), Arnold (20,851)

The 1863 red brick Classical Revival courthouse was remodeled in 1893 and enlarged in 1954 and 1975.  The courthouse is on a square at Main, Maple, First, and Locust Streets.  Charles H. Pond is the building designer.  The structure is on a hill and displays faux columns on the older section of the combined sections.  Missouri State Highway 21 Business is one block to the east of the site.  A Justice Center was added in 2008.  The county was organized on December 17, 1818 from parts of Sainte Genevieve and Saint Louis counties as the 10^th county.  It is named for United States President Thomas Jefferson.  He is also the namesake of the county seat of Cole County.  The county seat name is named for Jefferson’s home at Monticello using the English version of the estate’s name.  It is also the source for the county seat of Lewis County.  Herculaneum was the county seat from 1818-1839.  Jefferson County was the birthplace for 2 Missouri Governors, Thomas C. Fletcher and Jeremiah W. Nixon. 

Jefferson County government consists of a sheriff, an Executive, and 7 Council Members.  Six Circuit Court Judges and Six County Court Judges serve Jefferson County.  The county is in eastern Missouri on the Mississippi River border with Illinois.  Saint Louis, Missouri is directly north of the county.  The county center is 4 miles Northeast of Hillsboro.  The county is surrounded clockwise by Saint Louis County and Illinois and Sainte Genevieve, Saint Francois, Washington, and Franklin counties. 

The area of the county is 657 square miles.  It is 40 out of 115 in the state.  It ranks 7 out of 115 in population in the state.  It has a density of 344.9 persons per square mile making it 7 out of 115 in the state.  Jefferson County has 28.2% of its population in its incorporated areas.  Interstate Highway 55 travels north to south through the county from Saint Louis County to Sainte Genevieve County.  United States Highway 61 parallels Interstate Highway 55 from Saint Louis to Sainte Genevieve counties.  United States Highway 67 goes north to south from Saint Louis County to Saint Francois County.  The county is a backward comma.  Hillsboro is in the southern third of the county.  Arnold is in the northeast corner of the county.  Hillsboro is the county seat and Arnold is the largest city.  Hillsboro is 1.5% of the county population while Arnold is 9.2% of the county population.  This county is in the Saint Louis Metropolitan Statistical Area.