Mercer County, Illinois
Founding: 1835 (declared in 1825) Parent county: Unorganized territory Namesake: Hugh Mercer, Continental Army general Seat: Millersburg (1835–1857); Aledo (1857–) Land area: 561 square miles Population (2020): 15,699 Population (historic): 2,352 (1840); 15,042 (1860); 19,502 (1880); 20,945 (1900); 16,641 (1930) Periods of population growth: 1830–1880; 1890s; 1930s; 1960–1980 Subdivisions: Three cities; nine villages; 15 townships Pre-1940 residences (estimated): 2,941 (39.7%) Pre-1940 housing survival rate: 55.2% Pre-1860 housing survival rate (1940): 8.2% Farm housing in disrepair (1950): 5.1% Nonfarm housing in disrepair (1950): 5.9% Average farmhouse value (1930): $2,738 Average outbuilding value (1930): $2,795 Average farmhouse size (1940): 6.7 rooms Number of farms (1920): 2,022 Average farm size (1920): 129.7 acres Sources of settlement: ...