Calhoun County, Illinois in the context of "St. Louis Metropolitan Area"

Greater St. Louis is the 23rd-largest metropolitan statistical area (MSA) in the United States consisting with an MSA population more than 2.8 million, and almost 3 million CSA the largest in Missouri, and the second-largest in Illinois. Its core city—St. Louis, Missouri—sits in the geographic center of the metro area, on the west bank of the Mississippi River. The river bisects the metro area geographically between Illinois and Missouri, although the latter portion is much more populous. The MSA includes St. Louis County, which is independent of the City of St. Louis; their two populations are generally tabulated separately.

The St. Louis, MO-IL metropolitan statistical area (MSA) includes the City of St. Louis; the Illinois counties of Bond, Calhoun, Clinton, Jersey, Macoupin, Madison, Monroe, and St. Clair (known collectively as the Metro East); and the Missouri counties of Crawford (only the City of Sullivan), Franklin, Jefferson, Lincoln, St. Charles, St. Louis (separate from and not inclusive of the city of St. Louis), and Warren.

Hardin is a village and county seat of Calhoun County, Illinois, United States. The population was 801 at the 2020 census, down from 967 at the 2010 census.