- Population: 26,733 (Change since 1990: +0.7%)
- Created: February 25, 1847
- County seat: Harrisburg
- Largest town: Harrisburg (Pop. 9,860)
- Name origin: Saline Creek
- Beulah Heights (Unincorporated)
- Latitude & Longitude: 37°48'31" N, 88°27'15" W
- Elevation: 390
- Civil township: East Eldorado
- USGS Quad: Eldorado
- Buena Vista (Unincorporated)
- Latitude & Longitude: 37°44'18" N, 88°34'34" W
- Elevation: 402
- Civil township: Harrisburg
- USGS Quad: Harrisburg
- Carrier Mills (Village)
- Population: 1,886 (Change since 1990: -5.3%)
- Located on US 45 southwest of Harrisburg
- Latitude & Longitude: 37°41'03" N, 88°37'58" W
- Name origin: William H. Carrier
- Founded: November 19, 1872 by William H. Carrier
- Post office: Oct. 2, 1873 - Now
- Cottage Grove (Unincorporated)
- Alternate name: Cottagegrove
- Located just off IL 13 south of Eldorado
- Latitude & Longitude: 37°44'53" N, 88°24'38" W
- Survey: T. 9 S., R. 7 E., Sec. 10
- Elevation: 408
- Civil township: Cottage
- USGS Quad: Rudement
- Post office: Mar. 29, 1898 - Aug. 16, 1909 (Cottagegrove)
- Delta (Unincorporated)
- Latitude & Longitude: 37°41'03" N, 88°42'10" W
- Elevation: 410
- Civil township: Carrier Mills
- USGS Quad: Carrier Mills
- Derby (Unincorporated)
- Located east of Rudement in the southeastern
corner of the county
- Latitude & Longitude: 37°37'44" N, 88°23'08" W
- Survey: T. 10 S., R. 7 E., Sec. 24
- Elevation: 477
- Civil township: Mountain
- USGS Quad: Rudement
- Post office: Apr. 8, 1892 - Jun. 30, 1943
- Eagle (Unincorporated)
- Located north of Derby and east of Somerset
- Latitude & Longitude: 37°39'04" N, 88°23'34" W
- Survey: T. 10 S., R. 7 E., Sec. 13-14
- Elevation: 382
- Civil township: Mountain
- USGS Quad: Rudement
- Post office: Feb. 14, 1901 - Apr. 20, 1929
- Eldorado (City)
- Population: 4,534 (Change since 1990: -0.0%)
- Located at the intersection of US 45 and IL 142 northeast
of Harrisburg
- Latitude & Longitude: 37°48'49" N, 88°26'17" W
- Name origin: Samuel Elder + Joseph Reed
- Post office: Dec. 8, 1858 - Now
- Francis (Unincorporated)
- Located on IL 142 north of Eldorado near the Hamilton
County line
- Latitude & Longitude: 37°53'59" N, 88°27'11" W
- Survey: T. 7 S., R. 7 E.
- Elevation: 379
- Civil township: Rector
- USGS Quad: Broughton
- Post office: Aug. 26, 1893 - Oct. 31, 1919
- Galatia (Village)
- Population: 1,013 (Change since 1990: +3.1%)
- Located on IL 34 northwest of Harrisburg
- Latitude & Longitude: 37°50'26" N, 88°36'33" W
- Post office: Feb. 3, 1837 - Jun. 20, 1892 (Gallatia); Jun. 20, 1892 - Now (Galatia)
- Garden Heights (Unincorporated)
- Latitude & Longitude: 37°43'13" N, 88°31'37" W
- Elevation: 400
- Civil township: Harrisburg
- USGS Quad: Harrisburg
- Gaskins City (Unincorporated)
- Latitude & Longitude: 37°43'50" N, 88°31'35" W
- Elevation: 380
- Civil township: Harrisburg
- USGS Quad: Harrisburg
- Grayson (Historical)
- Halltown (Unincorporated)
- Alternate name: Hall Town
- Latitude & Longitude: 37°53'35" N, 88°41'25" W
- Elevation: 425
- Civil township: Tate
- USGS Quad: Akin
- Post office: Aug. 25, 1862 - Oct. 3, 1883 (Hall Town)
- Harco (Unincorporated)
- Located northwest of Harrisburg and southwest of Galatia
- Latitude & Longitude: 37°47'45" N, 88°39'00" W
- Survey: T. 8 S., R. 5 E.
- Elevation: 450
- Civil township: Brushy
- USGS Quad: Harco
- Post office: Nov. 21, 1917 - Oct. 1, 1971
- Harrisburg (City)
- Population: 9,860 (Change since 1990: +6.1%)
- Located near the intersections of US 45, IL 13, and IL 34
southwest of Eldorado and east of Marion
- Latitude & Longitude: 37°44'18" N, 88°32'26" W
- Post office: Apr. 25, 1848 - Now
- Horseshoe (Unincorporated)
- Located southwest of Cottage Grove near the Gallatin County line
- Latitude & Longitude: 37°41'56" N, 88°22'44" W
- Survey: T. 9 S., R. 7 E., Sec. 36
- Elevation: 364
- Civil township: Mountain
- USGS Quad: Rudement
- Post office: May 22, 1906 - Jul. 16, 1914
- Ledford (Unincorporated)
- Located between Harrisburg and Carrier Mills
on US 45
- Latitude & Longitude: 37°42'00" N, 88°35'24" W
- Survey: T. 9 S., R. 6 E.
- Elevation: 450
- Civil township: Harrisburg
- USGS Quad: Harrisburg
- Post office: Sep. 30, 1880 - Jan. 30, 1882; Feb. 20, 1892 - Oct. 31, 1935
- Liberty (Unincorporated)
- Located just west of Harrisburg
- Latitude & Longitude: 37°43'12" N, 88°34'18" W
- Survey: T. 9 S., R. 6 E.
- Elevation: 435
- Civil township: Harrisburg
- USGS Quad: Harrisburg
- Long Branch (Unincorporated)
- Located northeast of Galatia
- Latitude & Longitude: 37°53'06" N, 88°34'38" W
- Survey: T. 7 S., R. 6 E.
- Elevation: 428
- Civil township: Long Branch
- USGS Quad: Walpole
- Mitchellsville (Unincorporated)
- Located on IL 34 south of Harrisburg
- Latitude & Longitude: 37°39'02" N, 88°32'16" W
- Survey: T. 10 S., R. 6 E.
- Elevation: 385
- Civil township: Independence
- USGS Quad: Harrisburg
- Maps: 1878 and 1883 Tenney (Mitchellville P.O. or Independence)
- Muddy (Village)
- Population: 78 (Change since 1990: -10.3%)
- Located just northeast of Harrisburg
- Latitude & Longitude: 37°45'54" N, 88°30'60" W
- Post office: Sep. 22, 1908 - Now
- New Hope (Unincorporated)
- Located west of Harco
- Latitude & Longitude: 37°47'38" N, 88°41'20" W
- Survey: T. 8 S., R. 5 E.
- Elevation: 490
- Civil township: Brushy
- USGS Quad: Harco
- Post office: Apr. 7, 1892 - Sep. 30, 1907
- Newcastle (Unincorporated)
- Latitude & Longitude: 37°39'02" N, 88°40'17" W
- Elevation: 424
- Civil township: Carrier Mills
- USGS Quad: Carrier Mills
- Oldtown (Unincorporated)
- Located along the old Illinois Central railroad grade
southeast of Stonefort
- Latitude & Longitude: 37°36'08" N, 88°41'18" W
- Survey: T. 10 S., R. 5 E., Sec. 32
- Elevation: 437
- Civil township: Stonefort
- USGS Quad: Stonefort
- Pankeyville (Unincorporated)
- Located just south of Harrisburg on IL 34
- Latitude & Longitude: 37°42'30" N, 88°32'10" W
- Survey: T. 9 S., R. 6 E.
- Elevation: 385
- Civil township: Harrisburg
- USGS Quad: Harrisburg
- Raleigh (Village)
- Population: 330 (Change since 1990: +8.2%)
- Located between Galatia and Eldorado
- Latitude & Longitude: 37°49'37" N, 88°31'55" W
- Red Bud (Unincorporated)
- Alternate name: Brooklyn
- Located southeast of Eldorado
- Latitude & Longitude: 37°46'33" N, 88°24'19" W
- Survey: T. 8 S., R. 7 E.
- Elevation: 380
- Civil township: Cottage
- USGS Quad: Eldorado
- Map: 1883 Tenney
- Rileyville (Historical)
- Located on IL 34 northwest of Galatia
- Survey: T. 8 S., R. 5 E.
- Post office: Feb. 3, 1874 - Feb. 15, 1911
- Rudement (Unincorporated)
- Located along IL 34 southeast of Harrisburg
- Latitude & Longitude: 37°38'11" N, 88°29'25" W
- Survey: T. 10 S., R. 7 E., Sec. 24
- Elevation: 396
- Civil township: Independence
- USGS Quad: Rudement
- Post office: May 6, 1896 - Dec. 31, 1935
- Saline (Unincorporated)
- Latitude & Longitude: 37°38'43" N, 88°41'45" W
- Survey: T. 10 S., R. 5 E.
- Elevation: 407
- Civil township: Carrier Mills
- USGS Quad: Carrier Mills
- Saline City (Unincorporated)
- Latitude & Longitude: 37°49'25" N, 88°26'08" W
- Elevation: 430
- Civil township: East Eldorado
- USGS Quad: Eldorado
- Saline Valley Store (Unincorporated)
- Latitude & Longitude: 37°40'24" N, 88°29'56" W
- Elevation: 360
- Civil township: Independence
- USGS Quad: Rudement
- Somerset (Unincorporated)
- Located northeast of Rudement
- Latitude & Longitude: 37°39'16" N, 88°27'26" W
- Survey: T. 10 S., R. 7 E., Sec. 17
- Elevation: 450
- Civil township: Mountain
- USGS Quad: Rudement
- Map: 1878 (Mt. Airy)
- Stonefort (Village)
- Population: 292 (Change since 1990: -6.1%)
- Located between New Burnside and Carrier Mills
on US 45, straddling the Williamson-Saline County line
- Latitude & Longitude: 37°36'51" N, 88°42'29" W
- Post office: Feb. 15, 1858 - Now
- Texas City (Unincorporated)
- Located on US 45 northeast of Eldorado
- Latitude & Longitude: 37°52'42" N, 88°23'36" W
- Survey: T. 8 S., R. 7 E.
- Elevation: 367
- Civil township: Rector
- USGS Quad: Broughton
- Post office: Jul. 23, 1869 - Nov. 30, 1935
- Map: 1878 (Texas)
- Tison (Unincorporated)
- Located between Long Branch and Francis, northwest
of Eldorado
- Latitude & Longitude: 37°53'23" N, 88°30'52" W
- Survey: T. 7 S., R. 6 E.
- Elevation: 420
- Civil township: Long Branch
- USGS Quad: Walpole
- Post office: May 31, 1902 - Aug. 14, 1905
- Wasson (Unincorporated)
- Located on US 45 between Harrisburg and Eldorado
- Latitude & Longitude: 37°47'17" N, 88°29'05" W
- Elevation: 381
- Civil township: East Eldorado
- USGS Quad: Eldorado
- Post office: Apr. 25, 1908 - Dec. 31, 1918
- West End (Unincorporated)
- Loacted on IL 34 at the Franklin County line
- Latitude & Longitude: 37°53'24" N, 88°42'20" W
- Survey: T. 7 S., R. 5 E.
- Elevation: 430
- Civil township: Tate
- USGS Quad: Akin
- Post office: Aug. 26, 1881 - Jul. 31, 1955
- Whitesville (Unincorporated)
- Latitude & Longitude: 37°40'52" N, 88°27'50" W
- Elevation: 360
- Civil township: Mountain
- USGS Quad: Rudement (Not shown)
- Map: 1878
Name origin
Named after Saline Creek, in turn named for the salt
springs along it
| Year | Population | Percent change |
|---|
| 1850 | 5,588 | -- |
| 1860 | 9,322 | +66.8% |
| 1870 | 12,714 | +36.4% |
| 1880 | 15,940 | +25.4% |
| 1890 | 19,342 | +21.3% |
| 1900 | 21,685 | +12.1% |
| 1910 | 30,204 | +39.3% |
| 1920 | 38,353 | +27.0% |
| 1930 | 37,100 | -3.3% |
| 1940 | 38,066 | +2.6% |
| 1950 | 33,420 | -12.2% |
| 1960 | 26,227 | -21.5% |
| 1970 | 25,721 | -1.9% |
| 1980 | 28,448 | +10.6% |
| 1990 | 26,551 | -6.7% |
| 2000 | 26,733 | +0.7% |