This is a 4.2 percent rise in Petroleum County’s population, from 498 in 2020 to 519 in 2021.
Petroleum County had the 55th largest population in Montana in 2021.
The US Census Bureau found more than 73 percent of counties in the US saw a natural decrease in population in 2021. This is up from a 55.5 percent increase in 2020.
The Midwest suffered the most sustained population decreases, with many counties along the US East Coast and through the Rocky Mountains seeing increases.
The US population continues to grow, though at a slower rate than before.
Montana Counties By Population Change from 2020 to 2021
| County | 2020 Estimated Population | 2021 Estimated Population | % Change in Population From Year to Year |
|---|---|---|---|
| Mineral County | 4,565 | 4,860 | 6.5% |
| Broadwater County | 6,846 | 7,288 | 6.5% |
| Petroleum County | 498 | 519 | 4.2% |
| Sanders County | 12,451 | 12,959 | 4.1% |
| Lincoln County | 19,731 | 20,525 | 4% |
| Ravalli County | 44,351 | 45,959 | 3.6% |
| Flathead County | 104,773 | 108,454 | 3.5% |
| Carbon County | 10,512 | 10,847 | 3.2% |
| Garfield County | 1,172 | 1,209 | 3.2% |
| Musselshell County | 4,747 | 4,896 | 3.1% |
| Madison County | 8,657 | 8,917 | 3% |
| Jefferson County | 12,133 | 12,470 | 2.8% |
| Gallatin County | 119,502 | 122,713 | 2.7% |
| Lake County | 31,259 | 32,033 | 2.5% |
| Meagher County | 1,925 | 1,964 | 2% |
| Pondera County | 5,882 | 5,994 | 1.9% |
| Daniels County | 1,658 | 1,686 | 1.7% |
| Park County | 17,193 | 17,473 | 1.6% |
| Beaverhead County | 9,372 | 9,524 | 1.6% |
| Lewis and Clark County | 71,093 | 72,223 | 1.6% |
| Sweet Grass County | 3,671 | 3,723 | 1.4% |
| Fergus County | 11,457 | 11,617 | 1.4% |
| Prairie County | 1,076 | 1,091 | 1.4% |
| Golden Valley County | 820 | 831 | 1.3% |
| Judith Basin County | 2,017 | 2,044 | 1.3% |
| Yellowstone County | 165,045 | 167,146 | 1.3% |
| Missoula County | 118,238 | 119,533 | 1.1% |
| Granite County | 3,308 | 3,344 | 1.1% |
| Carter County | 1,413 | 1,428 | 1.1% |
| Toole County | 4,964 | 5,011 | 0.9% |
| Powell County | 6,934 | 6,999 | 0.9% |
| Treasure County | 761 | 768 | 0.9% |
| Silver Bow County | 35,168 | 35,411 | 0.7% |
| Wibaux County | 928 | 934 | 0.6% |
| Powder River County | 1,693 | 1,702 | 0.5% |
| Custer County | 11,859 | 11,916 | 0.5% |
| Teton County | 6,242 | 6,269 | 0.4% |
| Roosevelt County | 10,780 | 10,821 | 0.4% |
| Stillwater County | 9,010 | 9,044 | 0.4% |
| Chouteau County | 5,899 | 5,916 | 0.3% |
| Glacier County | 13,747 | 13,785 | 0.3% |
| Sheridan County | 3,518 | 3,527 | 0.3% |
| Cascade County | 84,328 | 84,511 | 0.2% |
| Phillips County | 4,190 | 4,192 | 0% |
| Valley County | 7,551 | 7,537 | -0.2% |
| Dawson County | 8,922 | 8,904 | -0.2% |
| Blaine County | 7,002 | 6,980 | -0.3% |
| Hill County | 16,250 | 16,179 | -0.4% |
| Fallon County | 3,033 | 3,017 | -0.5% |
| Liberty County | 1,960 | 1,946 | -0.7% |
| Big Horn County | 13,051 | 12,957 | -0.7% |
| McCone County | 1,733 | 1,718 | -0.9% |
| Wheatland County | 2,093 | 2,059 | -1.6% |
| Richland County | 11,501 | 11,283 | -1.9% |
| Rosebud County | 8,298 | 8,124 | -2.1% |
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