Sweetwater County, Wyoming

Sweetwater County is a county in Wyoming, United States, about 90 miles west of Rawlins along
Interstate 80. It had a population of 42,272 at the 2020 census, an estimated 41,267 by 2025, and
covers 10,427 square miles (27,010 km2) of land centred near 41°40′N 108°53′W — the largest
county by area in Wyoming and the eighth-largest in the country outside Alaska.

Green River is the county seat; its postal code is 82935. Rock Springs is the county’s largest
city. The county holds 2 cities, 4 incorporated towns and 13 census-designated places, plus a
handful of smaller unincorporated communities and ghost towns, and it runs on Mountain Time. Its
FIPS code is 56037.

Towns & Villages in Sweetwater County

Sweetwater County has 19 named places with regular Census recognition: 6 incorporated cities and
towns and 13 census-designated places (CDPs) with no local government of their own. CDP stands for
census designated place — a populated area the Census Bureau tracks without a municipal
charter. Population and ZIP figures marked — have no reliably current Census count.

Beyond those 19 places, the county carries several unincorporated communities with no CDP
boundary of their own — Blairtown, Creston, Quealy, Red Desert, Riner and Sweeney Ranch
— and a set of former settlements now counted as ghost towns: Bryan, Dines, Kanda, Linwood
(straddling the Utah line) and Winton. None has a current Census count or ZIP, so none is scored
in the table above.

Geography

Most of Sweetwater County sits inside the Great Divide Basin, a closed drainage basin where the
Continental Divide splits and rejoins, so no water in the basin’s interior reaches either ocean.
The Red Desert, a high-elevation sagebrush steppe, covers much of the northeast. The Green River
flows south through the county past its namesake city on its way to the Colorado River system, and
Flaming Gorge Reservoir touches the county’s southwest corner near the Utah line. Water makes up
about 0.6% of the county’s total area, roughly 170 km2 out of 27,170 km2 total.

Sweetwater County borders Fremont
County to the north, Carbon
County to the east, Moffat County,
Colorado to the south, Summit
County and Daggett County, Utah to
the southwest, Uinta County to the west,
and Lincoln County and
Sublette County to the northwest.

Demographics

Sweetwater County had a population of 42,272 at the 2020 census, the fourth-highest county total
in Wyoming, and an estimated 41,267 residents by 2025. Rock Springs and Green River together hold
more than four in five county residents; North Rock Springs, a CDP adjoining Rock Springs proper,
adds another 2,439. Countywide density works out to about 4.1 people per square mile, reflecting
the huge land area rather than a sparse population core — the two cities themselves are
comparatively dense. Wyoming’s statewide median household income was $72,415 in 2023, per the
Census Bureau’s American Community Survey.

Economy & Local Life

Trona mining anchors the county economy. The deposit beneath Green River is the largest known
trona reserve in the world, and several companies process it into soda ash for glass, detergent
and chemical manufacturing: Genesis Alkali, Tata Chemicals, Solvay, Ciner Wyoming and Church &
Dwight all operate mines or plants in the Green River Basin. Oil and natural gas wells across the
county add a second energy-sector income stream. Rock Springs also carries a coal-mining legacy
that drew Welsh, British, Irish and Scandinavian immigrant families in the 19th century, and it is
home to Western Wyoming Community College. Rock Springs hosts an annual International Festival and
Wyoming’s Big Show, both drawing visitors from across the region.

History

The county was organized on December 17, 1867, originally as Carter County within the Dakota
Territory, before Wyoming Territory itself existed. The Wyoming Territory legislature renamed it
Sweetwater County in 1869 for the Sweetwater River, which rises in the Wind River Range to the
north. Green River was platted by the Union Pacific Railroad in 1867 and incorporated the following
year; explorer John Wesley Powell launched his pioneering expedition down the Green and Colorado
rivers from the townsite on May 24, 1869. Rock Springs’ history includes a dark chapter: on
September 2, 1885, white miners attacked their Chinese coworkers in a dispute rooted in
anti-immigrant hostility over wages and jobs, killing at least 28 people in what is remembered as
the Rock Springs massacre.

Getting There

Interstate 80 runs the full width of the county west to east, joined by U.S. Highways 30 and 191
and Wyoming Highways 28, 370, 371, 372, 414, 430, 530 and 789. There is no interstate running
north–south through the county.

• Salt Lake City, Utah — about 180 miles west via I-80
• Cheyenne — about 215 miles east via I-80
• Denver, Colorado — about 260 miles southeast via I-80 and I-25
• Jackson — about 175 miles north via US-191

Rock Springs has its own commercial airport, Southwest Wyoming Regional Airport (RKS), with
service to Denver. Wyoming has had no scheduled Amtrak passenger service since 1997; the nearest
regular rail passenger connections run through Denver.

Frequently Asked Questions

Where is Sweetwater County, Wyoming?
It sits in the southwest part of Wyoming, bordering Colorado and Utah, along Interstate 80 between
Rawlins and the Utah state line.

What is the population of Sweetwater County?
Sweetwater County has a population of 42,272 according to the 2020 census, with an estimated 41,267
residents by 2025.

How big is Sweetwater County?
The county covers 10,427 square miles (27,010 km2) of land, making it the largest county by area in
Wyoming.

Which town is the county seat?
Green River is the county seat; its postal code is 82935.

How many towns and villages are in Sweetwater County?
The county has 19 Census-recognized places: 2 cities, 4 incorporated towns and 13 census-designated
places, plus several unincorporated communities and ghost towns with no formal boundary.

What ZIP codes serve Sweetwater County?
Principal ZIPs include 82935 and 82938 (Green River), 82901 and 82942 (Rock Springs), 82322
(Bairoil), 82934 (Granger), 82945 (Superior) and 82336 (Wamsutter).

Why is Sweetwater County important to the soda ash industry?
The trona deposit beneath Green River is the largest known in the world, and companies including
Genesis Alkali, Tata Chemicals and Solvay mine it there to make soda ash for glass and chemical
manufacturing worldwide.

More counties in this state: Towns and
villages in Wyoming.