- Population: 33,839 (Change since 1990: -2.2%)
- Created: October 5, 1795
- County seat: Chester
- Largest town: Chester (Pop. 5,185)
- Name origin: Edmund Randolph
- Baldwin (Village)
- Population: 3,627 (Change since 1990: +751.4%)
- Latitude & Longitude: 38°10'59" N, 89°50'33" W
- Blair (Unincorporated)
- Latitude & Longitude: 38°02'41" N, 89°44'31" W
- Elevation: 498
- Precinct: Blair
- USGS Quad: Steeleville
- Map: 1876 atlas
- Bremen (Unincorporated)
- Located on IL 150 northeast of Chester
- Latitude & Longitude: 37°58'16" N, 89°44'50" W
- Survey: T. 6 S., R. 6 W., Sec. 27, 34
- Elevation: 565
- Precinct: Bremen
- USGS Quad: Welge
- Chester (City)
- Population: 5,185 (Change since 1990: -36.7%)
- Located on the Mississippi River east of Kaskaskia
and opposite Claryville, MO
- Latitude & Longitude: 37°54'49" N, 89°49'19" W
- Collins (Unincorporated)
- Latitude & Longitude: 38°01'15" N, 89°56'52" W
- Elevation: 400
- Precinct: Ellis Grove
- USGS Quad: Evansville
- Coulterville (Village)
- Population: 1,230 (Change since 1990: +25.0%)
- Latitude & Longitude: 38°11'11" N, 89°36'20" W
- Danley (Unincorporated)
- Located along the railroad northwest of Prairie du Rocher
- Latitude & Longitude: 38°05'44" N, 90°06'56" W
- Elevation: 385
- Precinct: Prairie du Rocher
- USGS Quad: Prairie du Rocher
- Diamond Cross (Unincorporated)
- Latitude & Longitude: 37°59'04" N, 89°50'23" W
- Elevation: 618
- Precinct: Palestine
- USGS Quad: Chester (Not shown)
- Dozaville (Unincorporated)
- Alternate name: Pujol
- Located on Kaskaskia Island southwest of Kaskaskia
- Latitude & Longitude: 37°54'25" N, 89°57'23" W
- Elevation: 375
- Precinct: Kaskaskia
- USGS Quad: Kaskaskia
- Eden (Unincorporated)
- Latitude & Longitude: 38°07'14" N, 89°40'03" W
- Elevation: 530
- Precinct: Sparta
- USGS Quad: Steeleville
- Ellis Grove (Village)
- Population: 381 (Change since 1990: +7.9%)
- Latitude & Longitude: 38°00'32" N, 89°54'21" W
- Evansville (Village)
- Population: 724 (Change since 1990: -14.2%)
- Latitude & Longitude: 38°05'25" N, 89°56'18" W
- Ford (Historical)
- Latitude & Longitude: 37°52'31" N, 89°46'10" W
- Precinct: Chester
- USGS Quad: Chester (Not shown)
- Fort Gage (Unincorporated)
- Located along the Mississippi River northwest of Chester
- Latitude & Longitude: 37°57'38" N, 89°54'16" W
- Elevation: 390
- Precinct: Ellis Grove
- USGS Quad: Kaskaskia
- Grigg (Unincorporated)
- Latitude & Longitude: 38°11'26" N, 89°54'28" W
- Elevation: 421
- Precinct: Red Bud
- USGS Quad: Red Bud
- Houston (Unincorporated)
- Latitude & Longitude: 38°09'33" N, 89°46'52" W
- Elevation: 443
- Precinct: Baldwin
- USGS Quad: Baldwin
- Kampenville (Unincorporated)
- Latitude & Longitude: 38°01'10" N, 89°36'10" W
- Elevation: 510
- Precinct: Percy
- USGS Quad: Percy
- Kaskaskia (Village)
- Population: 9 (Change since 1990: -71.9%)
- Located on the west side of the Mississippi River west of Chester
and northeast of St. Mary, MO
- Latitude & Longitude: 37°55'17" N, 89°54'47" W
- Kellogg (Unincorporated)
- Previously known as: Forman, Missouri Junction, , and Mudds Landing
- Alternate name: Kellog
- Located opposite the Mississippi River from Little Rock, MO
- Latitude & Longitude: 38°00'57" N, 90°03'16" W
- Elevation: 380
- Precinct: Brewerville
- USGS Quad: Prairie du Rocher (Shows Kellogg and Mudds Landing)
- Leanderville (Unincorporated)
- Located south of Wine Hill
- Latitude & Longitude: 37°54'59" N, 89°40'34" W
- Survey: T. 7 S., R. 5 W., Sec. 17
- Elevation: 554
- Precinct: Wine Hill
- USGS Quad: Welge (Benchmark shown)
- Marigold (Unincorporated)
- Located on a county road east of Prairie du Rocher
- Latitude & Longitude: 38°04'47" N, 90°00'23" W
- Survey: T. 5 S., R. 8. W., Sec. 20
- Elevation: 564
- Precinct: Ruma
- USGS Quad: Prairie du Rocher
- Menard (Unincorporated)
- Latitude & Longitude: 37°54'36" N, 89°50'23" W
- Elevation: 500
- Precinct: Chester
- USGS Quad: Chester
- Modoc (Unincorporated)
- Latitude & Longitude: 38°02'31" N, 90°02'44" W
- Elevation: 392
- Precinct: Brewerville
- USGS Quad: Prairie du Rocher (Shows Modoc and Modoc Station)
- New Palestine (Unincorporated)
- Located at a crossroads north of Chester
- Latitude & Longitude: 37°59'47" N, 89°49'14" W
- Survey: T. 6 S., R. 7 W., Sec. 24
- Elevation: 580
- Precinct: Palestine
- USGS Quad: Chester
- Old Kaskaskia (Historical)
- Located north of Kaskaskia near the west bank
of the Mississippi River outside of the levee
- Latitude & Longitude: 37°56'56" N, 89°55'19" W
- Elevation: 388
- Precinct: Kaskaskia
- USGS Quad: Kaskaskia
- Percy (Village)
- Population: 942 (Change since 1990: +1.8%)
- Located on IL 150 east of Steeleville
- Latitude & Longitude: 38°00'59" N, 89°37'07" W
- Prairie (Unincorporated)
- Latitude & Longitude: 38°10'23" N, 89°56'35" W
- Elevation: 414
- Precinct: Red Bud
- USGS Quad: Red Bud
- Prairie du Rocher (Village)
- Population: 613 (Change since 1990: +13.5%)
- Latitude & Longitude: 38°04'59" N, 90°05'45" W
- Preston (Unincorporated)
- Latitude & Longitude: 38°06'22" N, 89°51'36" W
- Elevation: 490
- Precinct: Walsh
- USGS Quad: Walsh
- Randolph (Unincorporated)
- Located just south of New Bremen
- Latitude & Longitude: 37°57'60" N, 89°44'59" W
- Elevation: 567
- Precinct: Bremen
- USGS Quad: Welge (Benchmark shown)
- Map: 1876 atlas
- Red Bud (City)
- Population: 3,422 (Change since 1990: +17.3%)
- Located at intersection of IL 3, IL 154, and IL 159 near
the Monroe County line
- Latitude & Longitude: 38°12'42" N, 89°59'39" W
- Reily Lake (Unincorporated)
- Located northwest of Fort Gage
- Latitude & Longitude: 37°58'45" N, 89°55'15" W
- Elevation: 400
- Precinct: Ellis Grove
- USGS Quad: Kaskaskia
- Rockwood (Village)
- Population: 41 (Change since 1990: -8.9%)
- Located along IL 3
- Latitude & Longitude: 37°50'26" N, 89°42'02" W
- Roots (Unincorporated)
- Latitude & Longitude: 38°01'04" N, 89°58'20" W
- Elevation: 390
- Precinct: Brewerville
- USGS Quad: Evansville
- Ruma (Village)
- Population: 260 (Change since 1990: +1.6%)
- Latitude & Longitude: 38°08'06" N, 89°59'52" W
- Schuline (Unincorporated)
- Alternate name: Schulines
- Latitude & Longitude: 38°05'22" N, 89°46'44" W
- Elevation: 550
- Precinct: Central
- USGS Quad: Walsh
- Shiloh Hill (Unincorporated)
- Located between Wine Hill and Campbell Hill
- Latitude & Longitude: 37°55'31" N, 89°37'16" W
- Survey: T. 7 S., R. 5 W., Sec. 14
- Elevation: 520
- Precinct: Wine Hill
- USGS Quad: Willisville
- Sparta (City)
- Population: 4,486 (Change since 1990: -7.6%)
- Located near junction IL 4 and IL 154
- Latitude & Longitude: 38°07'23" N, 89°42'06" W
- Steeleville (Village)
- Population: 2,077 (Change since 1990: +0.9%)
- Located on IL 150 northeast of Chester
- Latitude & Longitude: 38°00'26" N, 89°39'30" W
- Tilden (Village)
- Population: 922 (Change since 1990: +0.3%)
- Latitude & Longitude: 38°12'43" N, 89°40'57" W
- Walsh (Unincorporated)
- Latitude & Longitude: 38°05'22" N, 89°51'03" W
- Elevation: 480
- Precinct: Walsh
- USGS Quad: Walsh
- Welge (Unincorporated)
- Located between Bremen and Wine Hill
- Latitude & Longitude: 37°57'23" N, 89°42'45" W
- Survey: T. 6 S., R. 6 W., Sec. 36
- Elevation: 410
- Precinct: Bremen
- USGS Quad: Welge
- Wine Hill (Unincorporated)
- Located between Welge and Shiloh Hill northeast of Chester
- Latitude & Longitude: 37°56'56" N, 89°40'28" W
- Survey: T. 7 S., R. 5 W., Sec. 5
- Elevation: 593
- Precinct: Wine Hill
- USGS Quad: Welge
- Map: 1876 atlas
Name origin
Named for Edmund Randolph, Revolutionary War soldier
and Attorney General under George Washington, among other things
| Year | Population | Percent change |
|---|
| 1820 | 3,492 | -- |
| 1830 | 4,429 | +26.8% |
| 1840 | 7,944 | +79.4% |
| 1850 | 11,079 | +39.5% |
| 1860 | 17,196 | +55.2% |
| 1870 | 20,859 | +21.3% |
| 1880 | 25,690 | +23.2% |
| 1890 | 25,049 | -2.5% |
| 1900 | 28,001 | +11.8% |
| 1910 | 29,120 | +4.0% |
| 1920 | 29,109 | -0.0% |
| 1930 | 29,313 | +0.7% |
| 1940 | 33,608 | +14.7% |
| 1950 | 31,673 | -5.8% |
| 1960 | 29,988 | -5.3% |
| 1970 | 31,379 | +4.6% |
| 1980 | 35,652 | +13.6% |
| 1990 | 34,583 | -3.0% |
| 2000 | 33,839 | -2.2% |