Williams County, North Dakota

Williams County is a county in North Dakota, United States, on the state’s western border with Montana, where the Bakken oil formation and the Missouri River both cross the landscape. It had a population of 40,950 at the 2020 census, making it the fifth-most populous county in North Dakota, and covers 2,077.6 square miles (5,381 km2) of land centred near 48°21′N 103°30′W.

Williston is the county seat, and its postal code is 58801. The county holds eight incorporated cities and roughly a dozen smaller unincorporated places, sits in the Central time zone, and carries FIPS code 38-105.

Towns & Villages in Williams County

Williston dominates the county by population; the rest of Williams County is a mix of small incorporated cities along the rail line and unincorporated farm communities scattered across the surrounding prairie.

ZIP Codes

• 58801 — Williston (also 58802 and 58803, PO Box only)
• 58852 — Tioga
• 58849 — Ray
• 58845 — Grenora
• 58843 — Epping
• 58795 — Wildrose
• 58830 — Alamo
• 58853 — Trenton (PO Box only)
• 58856 — Zahl
• 58755 — McGregor

Smaller places such as Springbrook, Wheelock, Buford, Corinth and Temple have no ZIP code of their own and are served by the nearest listed post office town.

Geography

Williams County sits on rolling prairie cut by the Missouri River, which forms part of the county’s southern edge, and by Lake Sakakawea backwater near the McKenzie County line. The northern half of the county is flatter cropland; the terrain roughens toward the river breaks in the south, where the Bakken shale formation underlies much of the county’s oil production. Of the county’s 2,148 total square miles, 2,077.6 square miles are land and 70.2 square miles (3.3%) are water.

Williams County borders:

• Divide County to the north
• Burke County to the northeast
• Mountrail County to the east
• McKenzie County to the south
• Roosevelt County, Montana, to the west
• Sheridan County, Montana, to the southwest

Demographics

The 2020 census counted 40,950 residents, up sharply from prior decades due to Bakken-era oil development; the 2025 estimate puts the county at roughly 41,767. Williston and Tioga are by far the two largest communities, together holding most of the county’s population. North Dakota’s statewide 2023 ACS median household income was $76,525; Williams County, driven by oilfield wages, has historically run above that figure. Outside Williston and Tioga, population density drops off quickly across the county’s farm townships.

Economy & Local Life

Oil and gas extraction from the Bakken and Three Forks formations is the county’s dominant industry, supported by trucking, oilfield services and rail terminals around Williston. Agriculture — wheat, canola and cattle — remains the base economy away from the oilfield. Williston State College and Trinity Health anchor the county seat’s non-energy employment. The Williston Basin Petroleum Conference draws industry visitors to the county each May, and the Williams County Fair runs each July in Williston.

History

Williams County was created on March 2, 1891, from part of Buford County, and organized soon after as settlement spread west along the Great Northern Railway line. It is named for Erastus Appleman Williams, a Dakota Territory legislator. The Fort Union Trading Post, an early-19th-century fur-trade post on the Missouri River near the Montana line, is preserved today as a national historic site within the county. Oil discoveries in the Bakken formation, first significant in the early 1950s and again from 2006 onward, reshaped the county’s population and economy.

Getting There

U.S. Highway 2 runs east–west through Williston and Ray; U.S. Highway 85 runs north–south through Williston toward Watford City. Williston Basin International Airport offers commercial air service; Amtrak’s Empire Builder stops at Williston station on its Chicago–Seattle/Portland route.

• Tioga — 28 miles east of Williston
• Ray — 15 miles north of Williston
• Watford City — 55 miles southeast of Williston
• Sidney, Montana — 45 miles southwest of Williston

Frequently Asked Questions

Where is Williams County, North Dakota?
It sits on North Dakota’s western border, directly across from Roosevelt and Sheridan counties in Montana.

What is the Williston postcode?
Williston’s main ZIP code is 58801, with 58802 and 58803 used for PO boxes.

What is the county seat of Williams County?
Williston is the county seat.

What was the population of Williams County at the 2020 census?
40,950, making it North Dakota’s fifth-most populous county.

What industry drives the local economy?
Oil and gas production from the Bakken formation, alongside wheat, canola and cattle farming.

Which counties border Williams County?
Divide, Burke, Mountrail and McKenzie counties in North Dakota, and Roosevelt and Sheridan counties in Montana.

Is there commercial air service in Williams County?
Yes, Williston Basin International Airport serves the county with commercial flights.

More counties in this state: Towns and villages in North Dakota.