Dahlgren is a village in Hamilton County, Illinois, United States. The population was 525 at the 2010 census. It is part of the Mount Vernon Micropolitan Statistical Area. Geography Dahlgren is located in northwestern Hamilton County at (38.199117, -88.685737). The mean elevation of the village is . Illinois Route 142 passes through the village, leading southeast to McLeansboro, the county seat, and northwest to Mount Vernon. According to the 2010 census, Dahlgren has a total area of , all land. History The area around present-day Dahlgren was known in the 1860s as the Shelton Precinct in Hamilton County before townships were formally established. In 1869 surveyors for the St. Louis & South-Eastern Rail Road (predecessor to the Louisville and Nashville Railroad) referred to the future town site as "Little Prairie." Construction of the railroad commenced in 1870 and was completed through the area in late 1871. At that time railroad officials applied to establish a post office in the nascent town which was to be home to the local railroad section boss. After the name "Cottonwood" was rejected by the U. S. postmaster (having already been used in Illinois) the name "Dahlgren" was assigned and the post office commenced operation on December 11, 1871. The village was named for John A. Dahlgren (1809–1870), a U.S. naval officer prominent during the American Civil War. On March 29, 1872, the official founding date of the village, A. M. Sturman executed a Deed of Dedication whereby he ceded 1 square mile of land centered on present day Main and 3rd Streets to formally layout the town. All land titles in Dahlgren derive from this original Deed of Dedication which was itself based on the original surveys conducted pursuant to Northwest Ordinance of 1787. The original settlement of Dahlgren extended roughly from the railroad depot/Chestnut St. (originally "A" Street) south to Sturmman St (originally "D" Street) and from 1st St. west to 5th St., a total of 12 square blocks. Demographics As of the census of 2010, there were 525 people, 211 households, and 140 families residing in the village. The population density was . There were 242 occupied housing units at an average density of . There are 31 unoccupied units. The racial makeup of the village was 96% White, 2.5% Black, and 1.5% Hispanic or Latino. There were 211 households, out of which 30.9% had children under the age of 18 living