- Population: 15,161 (Change since 1990: +2.8%)
- Created: March 3, 1843
- County seat: Metropolis
- Largest town: Metropolis (Pop. 6,482)
- Name origin: Fort Massac
- Ash Ridge (Historical)
- Located somewhere southeast of Belknap
- Latitude & Longitude: 37°15'06" N, 88°53'47" W
- Precinct: Hillerman
- USGS Quad: Karnak (Not shown)
- Maps: 1876 atlas and 1878
- Big Bay (Unincorporated)
- Alternate name: McNoel
- Located south of Reevesville
- Latitude & Longitude: 37°18'60" N, 88°43'18" W
- Survey: T. 14 S., R. 4 E., Sec. 12
- Elevation: 343
- Precinct: Benton
- USGS Quad: Reevesville
- Boaz (Unincorporated)
- Located just off IL 169, southeast of Belknap
- Latitude & Longitude: 37°17'30" N, 88°53'59" W
- Survey: T. 14 S., R. 3 E., Sec. 17
- Elevation: 370
- Precinct: Logan
- USGS Quad: Karnak
- Brookport (City)
- Population: 1,054 (Change since 1990: -1.5%)
- Located along US 45 opposite the Ohio River from Paducah
- Latitude & Longitude: 37°07'25" N, 88°37'49" W
- Choat (Unincorporated)
- Located on US 45 east of Joppa and northwest of Metropolis
- Latitude & Longitude: 37°12'48" N, 88°47'55" W
- Survey: T. 15 S., R. 4 E.
- Elevation: 384
- Precinct: Grant
- USGS Quad: Joppa
- Grinnell (Unincorporated)
- Located west of Mermet and southeast of Boaz
- Latitude & Longitude: 37°16'45" N, 88°52'20" W
- Survey: T. 14 S., R. 3 E.
- Elevation: 366
- Precinct: Logan
- USGS Quad: Mermet
- Hillerman (Unincorporated)
- Located northwest of Joppa
- Latitude & Longitude: 37°14'12" N, 88°53'23" W
- Survey: T. 15 S., R. 3 E.
- Elevation: 380
- Precinct: Hillerman
- USGS Quad: Bandana
- Map: 1856 Colton
- Joppa (Village)
- Population: 409 (Change since 1990: -16.9%)
- Located northwest of Metropolis
- Latitude & Longitude: 37°12'23" N, 88°50'41" W
- Post office: Jan. 5, 1874 - Now
- Massac City (Unincorporated)
- Latitude & Longitude: 37°08'37" N, 88°43'07" W
- Elevation: 335
- Precinct: Metropolis No. 4
- USGS Quad: Metropolis (Not shown)
- Mermet (Unincorporated)
- Located on US 45 north of Joppa
- Latitude & Longitude: 37°16'23" N, 88°50'46" W
- Survey: T. 14 S., R. 3 E.
- Elevation: 345
- Precinct: Logan
- USGS Quad: Mermet
- Metropolis (City)
- Population: 6,482 (Change since 1990: -3.7%)
- Located along US 45 northwest of Paducah
- Latitude & Longitude: 37°09'04" N, 88°43'55" W
- Metropolis Junction (Unincorporated)
- Midway (Unincorporated)
- Located northeast of Metropolis
- Latitude & Longitude: 37°14'23" N, 88°38'02" W
- Survey: T. 15 S., R. 5 E., Sec. 2
- Elevation: 548
- Precinct: Washington
- USGS Quad: Metropolis
- New Columbia (Unincorporated)
- Located northeast of Mermet and south of Ganntown
- Latitude & Longitude: 37°18'38" N, 88°46'31" W
- Survey: T. 14 S., R. 4 E., Sec. 9
- Elevation: 515
- Precinct: Georges Creek
- USGS Quad: Mermet
- Maps: 1856 Colton (George's Creek), 1876 atlas, and 1878
- Round Knob (Unincorporated)
- Located north of Metropolis
- Latitude & Longitude: 37°14'50" N, 88°44'15" W
- Survey: T. 15 S., R. 4 E., Sec. 2
- Elevation: 395
- Precinct: Grant
- USGS Quad: Metropolis
- Samoth (Unincorporated)
- Located between New Columbia and Ganntown, near
the Johnson County line
- Latitude & Longitude: 37°19'58" N, 88°47'15" W
- Survey: T. 14 S., R. 4 E.
- Elevation: 450
- Precinct: Georges Creek
- USGS Quad: Mermet
- Maps: 1876 atlas (Walnut Ridge) and 1883 Tenney (Walnut Ridge or Samoth P.O.)
- Shady Grove (Unincorporated)
- Located east of Brookport
- Latitude & Longitude: 37°07'26" N, 88°33'57" W
- Survey: T. 16 S., R. 6 E.
- Elevation: 345
- Precinct: Jackson
- USGS Quad: Paducah East
- Unionville (Unincorporated)
- Located just east of Shady Grove
- Latitude & Longitude: 37°07'20" N, 88°32'48" W
- Survey: T. 16 S., R. 6 E., Sec. 15-16
- Elevation: 370
- Precinct: Jackson
- USGS Quad: Paducah East
- Map: 1876 atlas (Union Village)
Name origin
Named for Fort Massac, derived from a French
surname, Massiac
| Year | Population | Percent change |
|---|
| 1850 | 4,092 | -- |
| 1860 | 6,204 | +51.6% |
| 1870 | 9,581 | +54.4% |
| 1880 | 10,443 | +9.0% |
| 1890 | 11,313 | +8.3% |
| 1900 | 13,110 | +15.9% |
| 1910 | 14,200 | +8.3% |
| 1920 | 13,559 | -4.5% |
| 1930 | 14,081 | +3.8% |
| 1940 | 14,937 | +6.1% |
| 1950 | 13,594 | -9.0% |
| 1960 | 14,341 | +5.5% |
| 1970 | 13,889 | -3.2% |
| 1980 | 14,990 | +7.9% |
| 1990 | 14,752 | -1.6% |
| 2000 | 15,161 | +2.8% |