Jerome County area

Population and density of Jerome County

The Census Bureau estimates that 26,362 people lived in Jerome County on July 1, 2025. That ranks #1,610 of 3,222 county equivalents nationally and #16 of 44 in Idaho. Since the April 1, 2020 estimates base of 24,241, the population has grown by 2,121 (+8.7%), compared with +10.4% for Idaho as a whole.

With 597.5 square miles of land, that is 44 people per square mile (17 per km²), placing Jerome County #1,663 nationally for density and #10 in Idaho. The median county equivalent has 47 people per square mile; the Idaho median is 10. Put another way, there are about 15 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 Jerome County

3 incorporated places lie at least partly in Jerome County. Together they are home to 14,964 people (56.8%); the other 11,398 (43.2%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Jerome city, with 13,731 residents in the county.

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Jerome County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.

Metropolitan area

Jerome County is an outlying county of the Twin Falls, ID Metropolitan Statistical Area. Its 2 county equivalents have 123,901 residents on 2,519.3 square miles of land; Jerome County accounts for 23.7% of the land and 21.3% of the residents. By combined land it ranks #130 of 393 metropolitan areas, and #333 by population.

ZIP codes

5 ZIP Code Tabulation Areas have land in Jerome County; 3 of them have most of their land inside the county, and the others mainly cover neighboring areas.

8330183325833358333883347

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 Jerome County

Jerome County shares a land border with 5 county equivalents. Each of them has more land than Jerome County. The largest neighbor is Cassia County (2,565.6 mi²) and the smallest is Gooding County (729.3 mi²). Together with its neighbors, Jerome County forms a block of 7,772.8 mi² of land, of which it holds 7.7%.

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

Jerome County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.7 times as much. Idaho’s county land could hold about 138 areas the size of Jerome County.

Another way to picture it: the same land area would fill a square about 24.4 miles (39.3 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 Jerome County?

Jerome County has more land than 1,587 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 Jerome County at #1,733 nationally by total area, 98 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 0.8%, compared with a national county-equivalent median of 1.2% — 0.3 percentage points lower. 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 Jerome 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.