Gem County area

Population and density of Gem County

The Census Bureau estimates that 21,773 people lived in Gem County on July 1, 2025. That ranks #1,785 of 3,222 county equivalents nationally and #19 of 44 in Idaho. Since the April 1, 2020 estimates base of 19,128, the population has grown by 2,645 (+13.8%), compared with +10.4% for Idaho as a whole.

With 559.8 square miles of land, that is 39 people per square mile (15 per km²), placing Gem County #1,772 nationally for density and #11 in Idaho. The median county equivalent has 47 people per square mile; the Idaho median is 10. Put another way, there are about 16 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 Gem County

1 incorporated place lies at least partly in Gem County. Together they are home to 8,900 people (40.9%); the other 12,873 (59.1%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Emmett city, with 8,900 residents in the county.

Metropolitan area

Gem County is an outlying county of the Boise City, ID Metropolitan Statistical Area. Its 5 county equivalents have 864,243 residents on 11,766.6 square miles of land; Gem County accounts for 4.8% of the land and 2.5% of the residents. By combined land it ranks #6 of 393 metropolitan areas, and #75 by population. It belongs to the Boise City-Mountain Home-Ontario, ID-OR Combined Statistical Area.

ZIP codes

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

83607836168361783629836368365783670

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 Gem County

Gem County shares a land border with 7 county equivalents. It has more land than 1 of them. The largest neighbor is Valley County (3,665.1 mi²) and the smallest is Payette County (406.9 mi²). Together with its neighbors, Gem County forms a block of 10,986.1 mi² of land, of which it holds 5.1%.

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

Gem County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.8 times as much. Idaho’s county land could hold about 148 areas the size of Gem County.

Another way to picture it: the same land area would fill a square about 23.7 miles (38.1 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 Gem County?

Gem County has more land than 1,371 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 Gem County at #1,955 nationally by total area, 104 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 0.9%, 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 Gem 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.