Dubuque County area

Population and density of Dubuque County

The Census Bureau estimates that 99,381 people lived in Dubuque County on July 1, 2025. That ranks #630 of 3,222 county equivalents nationally and #9 of 99 in Iowa. Since the April 1, 2020 estimates base of 99,280, the population has grown by 101 (+0.1%), compared with +1.5% for Iowa as a whole.

With 608.3 square miles of land, that is 163 people per square mile (63 per km²), placing Dubuque County #733 nationally for density and #8 in Iowa. The median county equivalent has 47 people per square mile; the Iowa median is 26. Put another way, there are about 3.9 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 Dubuque County

21 incorporated places lie at least partly in Dubuque County. Together they are home to 79,718 people (80.2%); the other 19,663 (19.8%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Dubuque city, with 59,148 residents in the county. Among places with at least 1,000 residents in 2020, Peosta city grew fastest since then (+16.4%).

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

Metropolitan area

Dubuque County is a central county of the Dubuque, IA Metropolitan Statistical Area. Dubuque County is the area’s only county equivalent, so the metro area has the same 608.3 square miles of land. By combined land it ranks #335 of 393 metropolitan areas, and #370 by population.

ZIP codes

20 ZIP Code Tabulation Areas have land in Dubuque County; 12 of them have most of their land inside the county, and the others mainly cover neighboring areas.

5200152002520035203152032520335203952040520455204652052520535205452056520655206852073520785207952237

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 Dubuque County

Dubuque County shares a land border with 6 county equivalents, including 2 in Wisconsin and Illinois. It has more land than 3 of them. The largest neighbor is Grant County (1,147.6 mi²) and the smallest is Jones County (575.6 mi²). Together with its neighbors, Dubuque County forms a block of 4,924.6 mi² of land, of which it holds 12.4%.

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

Dubuque 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. Iowa’s county land could hold about 92 areas the size of Dubuque County.

Another way to picture it: the same land area would fill a square about 24.7 miles (39.7 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 Dubuque County?

Dubuque County has more land than 1,626 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 Dubuque County at #1,690 nationally by total area, 94 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 1.3%, compared with a national county-equivalent median of 1.2% — 0.2 percentage points higher. 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 Dubuque 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.