- Population: 93,807 (Change since 1990: +16.4%)
- Created: December 11, 1818
- County seat: Union
- Largest town: Washington (Pop. 13,243)
- Name origin: Benjamin Franklin
- Anaconda (Unincorporated)
- Alternate name: Morrelton
- Located southwest of St. Clair
- Latitude & Longitude: 38°18'06" N, 91°02'26" W
- Survey: T. 41 N., R. 1 W., Sec. 9
- Elevation: 841
- Civil township: Central
- USGS Quad: Stanton
- Baltimore Settlement (Historical)
- Latitude & Longitude: 38°36'35" N, 91°14'30" W
- Survey: T. 45 N., R. 3 W., Sec. 34
- Elevation: 749
- Civil township: Boeuf
- USGS Quad: New Haven
- Beaufort (Unincorporated)
- Located at the crossing of US 50 and MO 185 east of Leslie
- Latitude & Longitude: 38°25'15" N, 91°11'20" W
- Elevation: 882
- Civil township: Lyon
- USGS Quad: Leslie
- Beemont (Unincorporated)
- Located on Route ZZ near the Gasconade County line
- Latitude & Longitude: 38°28'50" N, 91°21'33" W
- Survey: T. 43 N., R. 4 W., Sec. 10
- Civil township: Lyon
- USGS Quad: Gerald
- Benson Tourist City (Historical)
- Latitude & Longitude: 38°18'19" N, 91°04'02" W
- Survey: T. 41 N., R. 1 W., Sec. 7
- Elevation: 840
- Civil township: Central
- USGS Quad: Stanton
- Berger (Fourth-class city)
- Population: 206 (Change since 1990: -16.6%)
- Located on Route B east of Hermann
- Latitude & Longitude: 38°40'27" N, 91°20'19" W
- Post office: Apr. 15, 1856 - Now
- Boles (Unincorporated)
- Previously known as: Augusta Station
- Located on a county road off Route T west of Labadie
- Latitude & Longitude: 38°31'51" N, 90°53'24" W
- Survey: T. 44 N., R. 1 E., Secs. 27, 34
- Civil township: Boles
- USGS Quad: Washington East
- Boone (Historical)
- Latitude & Longitude: 38°15'33" N, 91°19'23" W
- Survey: T. 41 N., R. 4 W., Sec. 25
- Elevation: 850
- Civil township: Boone
- USGS Quad: Strain
- Calvey (Historical)
- Latitude & Longitude: 38°20'51" N, 90°47'46" W
- Survey: T. 42 N., R. 2 E., Sec. 27
- Elevation: 642
- Civil township: Calvey
- USGS Quad: Lonedell
- Campbellton (Unincorporated)
- Located on MO 185 near the intersection with Route KK
- Latitude & Longitude: 38°32'24" N, 91°09'38" W
- Survey: T. 44 N., R. 2 W., Sec. 28
- Civil township: Lyon
- USGS Quad: New Haven
- Caseyville (Unincorporated)
- Located just off MO 185 at the Washington County line near
Meramec State Park
- Latitude & Longitude: 38°12'19" N, 91°04'47" W
- Civil township: Meramec
- USGS Quad: Meramec State Park
- Catawissa (Unincorporated)
- Located at the junction of Route N and Route O southwest of Pacific
- Latitude & Longitude: 38°25'29" N, 90°46'57" W
- Survey: T. 43 N., R. 2 E., Sec. 34
- Elevation: 530
- Civil township: Calvey
- USGS Quad: Gray Summit
- Cedar Fork (Historical)
- Alternate name: Cedarfork
- Located northwest of Leslie
- Champion City (Unincorporated)
- Located on Route CC north of Route AC
- Latitude & Longitude: 38°19'10" N, 91°16'13" W
- Survey: T. 41 N., R. 3 W., Sec. 4
- Elevation: 752
- Civil township: Boone
- USGS Quad: Strain
- Clover Bottom (Unincorporated)
- Located on Route YY west of Krakow
- Latitude & Longitude: 38°30'13" N, 91°07'10" W
- Survey: T. 43 N., R. 2 W., Sec. 2
- Elevation: 681
- USGS Quad: Washington West
- Detmold (Unincorporated)
- Located on Route Y north of the junction with Route YY
- Latitude & Longitude: 38°32'34" N, 91°17'25" W
- Survey: T. 44 N., R. 3 W., Sec. 20
- Civil township: Lyon
- USGS Quad: Dissen
- Dissen (Unincorporated)
- Located on Route Y southwest of New Haven and northeast of Detmold
- Latitude & Longitude: 38°33'35" N, 91°16'33" W
- Survey: T. 44 N., R. 3 W., Sec. 15
- Civil township: Boeuf
- USGS Quad: Dissen
- Dundee (Unincorporated)
- Located just east of the junction of MO 100 and MO 185
- Latitude & Longitude: 38°35'36" N, 91°07'28" W
- Civil township: Boeuf
- USGS Quad: Washington West
- Elmont (Unincorporated)
- Located along Route H between Japan and Sullivan
- Latitude & Longitude: 38°14'08" N, 91°14'33" W
- Survey: T. 40 N., R. 3 W., Sec. 3
- Elevation: 974
- Civil township: Boone
- USGS Quad: Sullivan
- Etlah (Unincorporated)
- Located on Route B northwest of New Haven
- Latitude & Longitude: 38°38'21" N, 91°16'35" W
- Survey: T. 45 N., R. 3 W., Sec. 20
- Civil township: Boeuf
- USGS Quad: Berger
- Post office: 1864 - Aug. 15, 1935
- Fourmile Corner (Unincorporated)
- Located on Route A southwest of Washington
- Latitude & Longitude: 38°30'40" N, 91°02'46" W
- Elevation: 768
- USGS Quad: Washington West
- Fray (Historical)
- George (Historical)
- Latitude & Longitude: 38°14'43" N, 90°56'56" W
- Survey: T. 41 N., R. 1 E., Sec. 32
- Elevation: 542
- Civil township: Prairie
- USGS Quad: Cyclone Hollow
- Gerald (Fourth-class city)
- Population: 1,171 (Change since 1990: +31.9%)
- Located near the junction of US 50, Route Y, and Route H near the
Gasconade County line
- Latitude & Longitude: 38°23'59" N, 91°19'50" W
- Gildehouse (Unincorporated)
- Located just off Route V west of Villa Ridge
- Latitude & Longitude: 38°29'05" N, 90°56'18" W
- Survey: T. 43 N., R. 1 E., Sec. 8
- Civil township: Union
- USGS Quad: Moselle
- Gray Summit (Unincorporated)
- Population: 2,640 (2000 census)
- Latitude & Longitude: 38°29'23" N, 90°48'60" W
- Survey: T. 43 N., R. 2 E., Sec. 6
- Civil township: Boles
- USGS Quad: Gray Summit
- Named for Daniel Gray, who operated a hotel
starting about 1845. This area is a high point on the railroad.
- Source: Goodspeed (p. 338)
- Greenstreet (Unincorporated)
- Located at the end of a county road just southwest of Beaufort
- Latitude & Longitude: 38°24'23" N, 91°12'11" W
- Civil township: Boone
- USGS Quad: Leslie
- Hemker (Historical)
- Latitude & Longitude: 38°18'26" N, 90°46'39" W
- Survey: T. 41 N., R. 2 E., Sec. 11
- Elevation: 760
- Civil township: Prairie
- USGS Quad: Lonedell
- Hensley (Historical)
- Latitude & Longitude: 38°14'36" N, 90°52'15" W
- Survey: T. 41 N., R. 1 E., Sec. 36
- Elevation: 808
- Civil township: Prairie
- USGS Quad: Richwoods
- Huff (Historical)
- Latitude & Longitude: 38°14'37" N, 90°53'07" W
- Survey: T. 41 N., R. 1 E., Sec. 35
- Elevation: 792
- Civil township: Prairie
- USGS Quad: Cyclone Hollow
- Jaegers Shop (Historical)
- Latitude & Longitude: 38°27'40" N, 91°17'57" W
- Survey: T. 43 N., R. 3 W., Sec. 19
- Elevation: 817
- Civil township: Lyon
- USGS Quad: Gerald
- Japan (Unincorporated)
- Located near intersection of Route H and Route AR in the
southwest corner of the county
- Latitude & Longitude: 38°14'21" N, 91°18'21" W
- Survey: T. 40 N., R. 3 W., Sec. 6
- Elevation: 935
- Civil township: Boone
- USGS Quad: Argo
- Jeffriesburg (Unincorporated)
- Located west of Union on US 50
- Latitude & Longitude: 38°26'25" N, 91°05'17" W
- Elevation: 762
- Civil township: Union
- USGS Quad: Union
- Kent (Historical)
- Located along the Missouri River east of New Haven
- Latitude & Longitude: 38°35'54" N, 91°09'03" W
- Survey: T. 44 N., R. 2 W., Sec. 4
- Elevation: 500
- Civil township: Boeuf
- USGS Quad: New Haven
- Kiel (Unincorporated)
- Located on Route C just north of Route YY
- Latitude & Longitude: 38°31'18" N, 91°14'37" W
- Survey: T. 44 N., R. 3 W., Sec. 34
- Elevation: 755
- Civil township: Lyon
- USGS Quad: New Haven
- Kohl City (Unincorporated)
- Located on Kohl City Road off Route VV at the Gasconade County line
- Latitude & Longitude: 38°35'54" N, 91°21'52" W
- Elevation: 622
- Civil township: Boeuf
- USGS Quad: Dissen
- Krakow (Unincorporated)
- Located at the intersection of Route A and Route YY northwest of Union
- Latitude & Longitude: 38°29'51" N, 91°02'44" W
- Survey: T. 43 N., R. 1 W., Sec. 8
- Elevation: 764
- Civil township: Union
- USGS Quad: Union
- Labadie (Unincorporated)
- Located at the intersection of Route T and Route MM northeast of Gray Summit
- Latitude & Longitude: 38°31'44" N, 90°50'60" W
- Elevation: 526
- Civil township: Boles
- USGS Quad: Labadie
- Leslie (Village)
- Population: 87 (Change since 1990: -35.1%)
- Located at the junction of US 50 and Route CC east of Gerald
- Latitude & Longitude: 38°25'04" N, 91°13'55" W
- Lonedell (Unincorporated)
- Alternate name: Lone Dell
- Located at the junction of MO 30 and Route FF
- Latitude & Longitude: 38°18'29" N, 90°49'39" W
- Survey: T. 41 N., R. 2 E., Sec. 8
- Civil township: Prairie
- USGS Quad: Lonedell
- Luebbering (Unincorporated)
- Located along Route FF south of Lonedell
- Latitude & Longitude: 38°16'13" N, 90°49'09" W
- Survey: T. 41 N., R. 2 E., Sec. 20
- Elevation: 759
- Civil township: Prairie
- USGS Quad: Lonedell
- Named for John F. Luebbering, postmaster
- Source: Ramsay (p. 68)
- Lyon (Unincorporated)
- Located on MO 185 north of the junction with Route YY
- Latitude & Longitude: 38°30'42" N, 91°10'26" W
- Civil township: Lyon
- USGS Quad: New Haven
- Maupin (Historical)
- Latitude & Longitude: 38°14'26" N, 90°47'02" W
- Survey: T. 40 N., R. 2 E., Sec. 3
- Elevation: 620
- Civil township: Prairie
- USGS Quad: Richwoods
- Meramec Terrace (Historical)
- Latitude & Longitude: 38°24'57" N, 90°49'48" W
- Survey: T. 42 N., R. 2 E., Sec. 5
- Elevation: 500
- Civil township: Calvey
- USGS Quad: Gray Summit
- Miramiguoa Park (Village)
- Population: 127 (2000 census)
- Latitude & Longitude: 38°14'20" N, 91°04'07" W
- Monday (Historical)
- Latitude & Longitude: 38°12'60" N, 91°01'16" W
- Survey: T. 40 N., R. 1 W., Sec. 10
- Civil township: Meramec
- USGS Quad: Meramec State Park
- Moselle (Unincorporated)
- Formerly incorporated
- Located at the end of Route AH
- Latitude & Longitude: 38°23'12" N, 90°53'52" W
- Survey: T. 42 N., R. 1 E., Sec. 15
- Elevation: 493
- Civil township: Central
- USGS Quad: Moselle
- Mount Hope (Unincorporated)
- Alternate name: Mounthope
- Located on MO 47 just south of MO 30
- Latitude & Longitude: 38°17'54" N, 90°52'25" W
- Elevation: 703
- Civil township: Prairie
- USGS Quad: Lonedell
- Neier (Unincorporated)
- Located on Neier Road, beyond the end of Route UU
- Latitude & Longitude: 38°23'28" N, 91°06'37" W
- Survey: T. 42 N., R. 2 W., Sec. 14
- Elevation: 816
- Civil township: Union
- USGS Quad: Union
- New Haven (Fourth-class city)
- Population: 1,867 (Change since 1990: +6.3%)
- Latitude & Longitude: 38°36'30" N, 91°13'08" W
- Founded: 1856
- Oak Grove Village (Village)
- Population: 382 (Change since 1990: -5.0%)
- Located outside of Sullivan
- Latitude & Longitude: 38°13'32" N, 91°09'04" W
- Oetters (Unincorporated)
- Located along Route T between Labadie and St. Albans
- Latitude & Longitude: 38°33'19" N, 90°47'37" W
- Survey: T. 44 N., R. 2 E., Sec. 16
- Elevation: 486
- Civil township: Boles
- USGS Quad: Labadie
- Pacific (Fourth-class city)
- Population: 5,482 (Change since 1990: +26.0%)
- Located along I-44 near the St. Louis County line
- Latitude & Longitude: 38°28'55" N, 90°44'29" W
- Founded: November 29, 1852 as Franklin
- Parkway (Village)
- Population: 280 (Change since 1990: +1.1%)
- Located just southeast of St. Clair
- Latitude & Longitude: 38°20'17" N, 90°58'11" W
- Petersville (Unincorporated)
- Located on a county road northeast of St. Albans
- Latitude & Longitude: 38°35'14" N, 90°44'48" W
- Civil township: Boles
- USGS Quad: Eureka
- Piney Park (Unincorporated)
- Formerly incorporated
- Located along Route K southeast of St. Clair
- Latitude & Longitude: 38°18'04" N, 90°56'34" W
- Survey: T. 41 N., R. 1 E., Secs. 8, 17
- Elevation: 743
- Civil township: Central
- USGS Quad: Saint Clair
- Pohlman Mill (Historical)
- Latitude & Longitude: 38°27'38" N, 90°57'54" W
- Survey: T. 43 N., R. 1 W., Sec. 24
- Civil township: Union
- USGS Quad: Moselle
- Port Hudson (Unincorporated)
- Located at the intersection of Route C and Old State Road northwest of Leslie
- Latitude & Longitude: 38°27'14" N, 91°15'14" W
- Survey: T. 43 N., R. 3 W., Sec. 22
- Civil township: Lyon
- USGS Quad: Gerald
- Prater (Unincorporated)
- Located at the railroad bridge over the Meramec River
south of Pacific
- Latitude & Longitude: 38°26'58" N, 90°45'35" W
- Elevation: 469
- Civil township: Boles
- USGS Quad: Gray Summit
- Robertsville (Unincorporated)
- Located at the junction of Route O and Route N south of Gray Summit
- Latitude & Longitude: 38°24'53" N, 90°48'50" W
- Civil township: Calvey
- USGS Quad: Gray Summit
- Senate Grove (Historical)
- Latitude & Longitude: 38°34'32" N, 91°19'40" W
- Survey: T. 44 N., R. 4 W., Sec. 12
- Elevation: 765
- Civil township: Boeuf
- USGS Quad: Dissen
- Shotwell (Historical)
- South Point (Historical)
- Located along the river east of Washington
- Latitude & Longitude: 38°32'38" N, 90°58'42" W
- Survey: T. 44 N., R. 1 W., Sec. 25
- Elevation: 540
- Civil township: Washington
- USGS Quad: Washington East
- Spring Bluff (Unincorporated)
- Alternate name: Springbluff
- Located at the intersection of MO 185 and Route AC northwest of Sullivan
- Latitude & Longitude: 38°17'44" N, 91°14'16" W
- Survey: T. 41 N., R. 3 W., Sec. 14
- Elevation: 910
- Civil township: Boone
- USGS Quad: Spring Bluff
- St. Albans (Unincorporated)
- Latitude & Longitude: 38°34'45" N, 90°46'30" W
- Survey: T. 44 N., R. 2 E., Sec. 2
- Civil township: Boles
- USGS Quad: Labadie
- St. Clair (Fourth-class city)
- Population: 4,390 (Change since 1990: +12.1%)
- Latitude & Longitude: 38°20'43" N, 90°58'51" W
- Founded: January 14, 1859 by William Kerr
- Stanton (Unincorporated)
- Located near the interchange of I-44, Route JJ, and Route W northeast of Sullivan
- Latitude & Longitude: 38°16'28" N, 91°06'20" W
- Survey: T. 41 N., R. 2 W., Secs. 23-26,
- Elevation: 872
- Civil township: Meramec
- USGS Quad: Stanton
- Strain (Unincorporated)
- Located near the junction of Route H and Route AC northwest of Sullivan
- Latitude & Longitude: 38°17'30" N, 91°18'10" W
- Survey: T. 41 N., R. 3 W., Sec. 18
- Civil township: Boone
- USGS Quad: Strain
- Sullivan (Fourth-class city)
- Population: 6,351 (Change since 1990: +12.2%)
- Located near I-44 next to the Crawford County line
- Latitude & Longitude: 38°12'29" N, 91°09'37" W
- Name origin: Stephen Sullivan
- Founded: 1859 by Stephen Sullivan
- Tavern Rock (Historical)
- Located along the Missouri River in the far northeast
corner of the county
- USGS Quad: Labadie
- The Diamonds (Historical)
- Latitude & Longitude: 38°28'23" N, 90°51'24" W
- Survey: T. 43 N., R. 1 E., Sec. 13
- Elevation: 800
- Civil township: Boles
- USGS Quad: Gray Summit
- Twin Springs (Unincorporated)
- Located on the Meramec River near Stanton
- Latitude & Longitude: 38°16'19" N, 91°04'25" W
- Civil township: Central
- USGS Quad: Stanton
- Union (Fourth-class city)
- Population: 7,757 (Change since 1990: +31.3%)
- Located near the crossing of US 50 and MO 47
- Latitude & Longitude: 38°27'00" N, 91°00'30" W
- Villa Ridge (Unincorporated)
- Population: 2,417 (2000 census)
- Located on Route M just south of MO 100
- Latitude & Longitude: 38°28'21" N, 90°53'12" W
- Survey: T. 43 N., R. 1 E., Secs. 14-15
- Elevation: 637
- Civil township: Boles
- USGS Quad: Moselle
- Walbert (Historical)
- Latitude & Longitude: 38°19'48" N, 91°19'54" W
- Survey: T. 41 N., R. 4 W.
- Elevation: 744
- Civil township: Boone
- USGS Quad: Strain
- Washington (Third-class city)
- Population: 13,243 (Change since 1990: +23.7%)
- Located near the MO 47 crossing of the Missouri River
- Latitude & Longitude: 38°33'29" N, 91°00'43" W
- Name origin: George Washington
| Year | Population | Percent change |
|---|
| 1830 | 3,484 | -- |
| 1840 | 7,515 | +115.7% |
| 1850 | 11,021 | +46.7% |
| 1860 | 18,085 | +64.1% |
| 1870 | 30,098 | +66.4% |
| 1880 | 26,534 | -11.8% |
| 1890 | 28,056 | +5.7% |
| 1900 | 30,581 | +9.0% |
| 1910 | 29,830 | -2.5% |
| 1920 | 28,427 | -4.7% |
| 1930 | 30,519 | +7.4% |
| 1940 | 33,868 | +11.0% |
| 1950 | 36,046 | +6.4% |
| 1960 | 44,566 | +23.6% |
| 1970 | 55,116 | +23.7% |
| 1980 | 71,233 | +29.2% |
| 1990 | 80,603 | +13.2% |
| 2000 | 93,807 | +16.4% |