Petroleum County area

Population and density of Petroleum County

The Census Bureau estimates that 548 people lived in Petroleum County on July 1, 2025. That ranks #3,214 of 3,222 county equivalents nationally and #56 of 56 in Montana. Since the April 1, 2020 estimates base of 498, the population has grown by 50 (+10%), compared with +5.6% for Montana as a whole.

With 1,655.6 square miles of land, that is 0.33 people per square mile (0.13 per km²), placing Petroleum County #3,206 nationally for density and #55 in Montana. The median county equivalent has 47 people per square mile; the Montana median is 2.8. Put another way, there are about 1,934 acres of land per resident.

U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.

Cities and towns in Petroleum County

1 incorporated place lies at least partly in Petroleum County. Together they are home to 205 people (37.4%); the other 343 (62.6%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Winnett town, with 205 residents in the county.

Metropolitan area

Petroleum County is not part of any metropolitan or micropolitan statistical area in the Office of Management and Budget’s July 2023 delineation; 1,306 other county equivalents are also outside one. These areas are built around an urban core of at least 10,000 people plus the counties tied to it by commuting, so counties outside them are generally rural.

ZIP codes

4 ZIP Code Tabulation Areas have land in Petroleum County; 1 of them have most of their land inside the county, and the others mainly cover neighboring areas.

59032590585907259087

ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.

Counties bordering Petroleum County

Petroleum County shares a land border with 5 county equivalents. Each of them has more land than Petroleum County. The largest neighbor is Phillips County (5,140.4 mi²) and the smallest is Musselshell County (1,869 mi²). Together with its neighbors, Petroleum County forms a block of 22,689 mi² of land, of which it holds 7.3%.

How big is Petroleum County compared with U.S. states?

Petroleum County has more land than 1 of the 50 states. It is about 1.6 times the land area of Rhode Island (1,033.9 mi²), while Delaware, the next larger state, has 1.2 times as much land (1,948.6 mi²). Montana’s county land could hold about 88 areas the size of Petroleum County.

Another way to picture it: the same land area would fill a square about 40.7 miles (65.5 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.

State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.

What stands out about Petroleum County?

Petroleum County has more land than 2,856 of the other 3,221 county equivalents in the dataset.

A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.

Does including water change its rank?

Using land plus water places Petroleum County at #402 nationally by total area, 36 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.

Its water share is 1.1%, compared with a national county-equivalent median of 1.2%. The two percentages are within 0.1 percentage points of each other. This describes the statistical geography’s land/water mix, not flood exposure or developable land.

Closest positions in the national land ranking

These entries sit immediately beside Petroleum County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.