County outline
Where Phelps County is located
Area breakdown
Land accounts for 99.6% of Phelps County’s measured area and water for 0.4%. Its combined area converts to 1,746.5 square kilometers or approximately 431,566 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 671.787 | 1,739.92 | 429,943.7 |
| Water | 2.535 | 6.566 | 1,622.4 |
| Total | 674.322 | 1,746.486 | 431,566.1 |
How Phelps County compares
By original Census land area, Phelps County ranks #37 of 115 in Missouri and #1404 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 1.135 times the Missouri county-equivalent median of 592 square miles. It accounts for 1% of the combined county land area in the state.
See the complete Missouri ranking · What counts as a county equivalent?
Population and density of Phelps County
The Census Bureau estimates that 45,247 people lived in Phelps County on July 1, 2025. That ranks #1,106 of 3,222 county equivalents nationally and #24 of 115 in Missouri. Since the April 1, 2020 estimates base of 44,634, the population has grown by 613 (+1.4%), compared with +1.9% for Missouri as a whole.
With 671.8 square miles of land, that is 67 people per square mile (26 per km²), placing Phelps County #1,287 nationally for density and #27 in Missouri. The median county equivalent has 47 people per square mile; the Missouri median is 31. Put another way, there are about 9.5 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 44,553 | 44,891 | 45,196 | 45,285 | 45,206 | 45,247 |
| Change | — | +338 | +305 | +89 | −79 | +41 |
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 Phelps County
5 incorporated places lie at least partly in Phelps County. Together they are home to 25,605 people (56.6%); the other 19,642 (43.4%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is Rolla city, with 20,588 residents in the county. Among places with at least 1,000 residents in 2020, Rolla city grew fastest since then (+3.3%).
| Incorporated place | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Rolla cityCounty seat | 20,588 | +3.3% | 12.1 |
| St. James city | 3,925 | +0.3% | 4.241 |
| Doolittle city | 565 | −0.2% | 2.784 |
| Newburg city | 331 | −1.5% | 0.646 |
| Edgar Springs city | 196 | −0.5% | 0.469 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Phelps County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.
Metropolitan area
Phelps County is a central county of the Rolla, MO Micropolitan Statistical Area. Phelps County is the area’s only county equivalent, so the micro area has the same 671.8 square miles of land. By combined land it ranks #324 of 542 micropolitan areas, and #271 by population.
ZIP codes
12 ZIP Code Tabulation Areas have land in Phelps County; 7 of them have most of their land inside the county, and the others mainly cover neighboring areas.
654016540965436654496545965461654626552965542655506555965560
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 Phelps County
Phelps County shares a land border with 6 county equivalents. It has more land than 3 of them. The largest neighbor is Texas County (1,177.3 mi²) and the smallest is Gasconade County (519 mi²). Together with its neighbors, Phelps County forms a block of 4,937.4 mi² of land, of which it holds 13.6%.
| Bordering county equivalent | Land mi² | Size vs. Phelps | Compare |
|---|---|---|---|
| Texas County | 1,177.3 | 1.8× larger | Compare |
| Dent County | 752.8 | 1.1× larger | Compare |
| Crawford County | 742.5 | 1.1× larger | Compare |
| Pulaski County | 547.2 | 1.2× smaller | Compare |
| Maries County | 526.9 | 1.3× smaller | Compare |
| Gasconade County | 519 | 1.3× smaller | Compare |
How big is Phelps County compared with U.S. states?
Phelps County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.5 times as much. Missouri’s county land could hold about 102 areas the size of Phelps County.
Another way to picture it: the same land area would fill a square about 25.9 miles (41.7 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 Phelps County?
Phelps County has more land than 1,818 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 Phelps County at #1,509 nationally by total area, 105 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 0.4%, compared with a national county-equivalent median of 1.2% — 0.8 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 Phelps County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #1403 | Pike County, Alabama | 672.1 | Compare |
| #1404 | Phelps County, Missouri | 671.8 | This county |
| #1405 | Pike County, Missouri | 670.4 | Compare |
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.
Representative coordinates
The Census internal point is 37.866326, -91.790350. It represents a location inside the geography; it is not necessarily the centroid or the address of a courthouse.
Source and precision
U.S. Census Bureau, 2026 Gazetteer Files, Counties. Original ALAND: 1,739,921,104 m²; AWATER: 6,564,991 m². Rankings use ALAND; exact ties use ascending GEOID. Tables preserve Census-published square miles to three decimals, with conversions based on those values.
Common questions
How big is Phelps County?
Phelps County, Missouri has 671.8 square miles (1,739.9 km²) of land and 2.535 square miles of water, for a total area of 674.3 square miles. It ranks #1404 of 3,222 U.S. county equivalents by land area.
Is Phelps County the largest county in Missouri?
No. Phelps County ranks #37 of 115 in Missouri by land area. The largest is Texas County, with 1,177.3 square miles of land.
What counties border Phelps County?
Phelps County shares a land border with Dent County, Pulaski County, Maries County, Crawford County, Texas County, and Gasconade County.
What is the population of Phelps County?
The Census Bureau estimates Phelps County had 45,247 residents on July 1, 2025, ranking #1,106 of 3,222 county equivalents. That is 67 people per square mile of land.
What is the county seat of Phelps County?
The county seat of Phelps County is Rolla.
What cities and towns are in Phelps County?
Phelps County has 5 incorporated places. The most populous are Rolla city, St. James city, Doolittle city, Newburg city, and Edgar Springs city; 19,642 residents live outside any incorporated place.
Is Phelps County part of a metropolitan area?
Yes. It is a central county of the Rolla, MO Micropolitan Statistical Area.
How many ZIP codes are in Phelps County?
12 ZIP Code Tabulation Areas have land in Phelps County, and 7 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Phelps County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 1.5 times as much land.
How many acres of land are in Phelps County?
The land measurement converts to approximately 429,944 acres. Including water, total area is approximately 431,566 acres. One square mile equals 640 acres.
Why might another source show a different area?
Check whether it reports land or total area, its Census vintage, and its rounding. Our guide explains how to reconcile county area figures.
Can this establish a property boundary?
No. Statistical measurements and generalized maps do not establish property lines. Consult the relevant local surveying or land-records authority.