Boulder County, Colorado
County seat: Boulder · Population 328,560 (2025) · 726 sq mi
Boulder County is the 9th most populous of Colorado's 64 counties, with 328,560 people (2025 estimate). Its county seat is Boulder. It is part of the Region 3: Denver Metropolitan Area region, one of the 14 Planning and Management Regions of Colorado. The map shows its 10 cities and towns and the 6 neighboring counties.
Boulder County facts
- County seat
- Boulder
- Population (2025 estimate)
- 328,560 −0.7% since 2020
- Land area
- 726 sq mi 52nd largest of 64
- Water area
- 14 sq mi
- Population density
- 452 per sq mi
- Established
- 1861
- Named after
- Boulder, Boulder Creek
- Largest city
- Boulder 105,689
- Median household income
- $103,994
- Cities and towns
- 10 plus 24 CDPs
- ZIP codes
- 23
- Time zone
- Mountain
- FIPS code
- 08013
Cities and towns in Boulder County
Boulder County has 10 incorporated cities, towns and villages. Populations count the people living inside Boulder County; cities that cross a county line also list the other counties.
| Name | Type | Population 2025 | Also in |
|---|---|---|---|
| Boulder (county seat) | City | 105,689 | |
| Longmont | City | 98,807 | Weld County |
| Lafayette | City | 30,116 | |
| Louisville | City | 20,581 | |
| Erie | Town | 15,395 | Weld County |
| Superior | Town | 13,637 | Jefferson County |
| Lyons | Town | 2,119 | |
| Nederland | Town | 1,463 | |
| Jamestown | Town | 245 | |
| Ward | Town | 124 |
Unincorporated communities (CDPs)
Census-designated places are communities without their own city government; the county provides their services.
| Community | Population | Also in |
|---|---|---|
| Gunbarrel | 10,051 | |
| Niwot | 3,447 | |
| Allenspark | 825 | |
| Lazy Acres | 778 | |
| Paragon Estates | 667 | |
| Altona | 587 | |
| Pine Brook Hill | 543 | |
| Sugarloaf | 474 | |
| Eldora | 465 | |
| St. Ann Highlands | 453 | |
| Coal Creek | 394 | Gilpin and Jefferson counties |
| Tall Timber | 382 | |
| Sunshine | 330 | |
| Eldorado Springs | 320 | |
| Crisman | 268 | |
| Bar-K Ranch | 199 | |
| Seven Hills | 183 | |
| Mountain Meadows | 180 | |
| Gold Hill | 178 | |
| Glendale | 69 | |
| Bonanza Mountain Estates | 56 | |
| Hidden Lake | 29 | |
| Valmont | 27 | |
| Leyner | 0 |
ZIP codes in Boulder County
23 ZIP codes reach into Boulder County. ZIP codes ignore county lines, so some also cover a neighboring county.
- 80020 also Broomfield, Jefferson and Adams counties
- 80025
- 80026 also Broomfield County
- 80027
- 80301
- 80302
- 80303
- 80304
- 80305
- 80310
- 80403 also Jefferson and Gilpin counties
- 80455
- 80466
- 80471
- 80481
- 80501
- 80503 also Larimer County
- 80504 also Weld and Larimer counties
- 80510
- 80513 also Larimer and Weld counties
- 80516 also Weld and Broomfield counties
- 80540 also Larimer County
- 80544
Population of Boulder County, 2020–2025
Boulder County shrank by 2,201 people (−0.7%) between April 2020 and July 2025: 1,379 more births than deaths and a net loss of 3,300 people from migration.
| Year (July 1) | Population |
|---|---|
| 2020 | 330,982 |
| 2021 | 327,325 |
| 2022 | 327,914 |
| 2023 | 327,945 |
| 2024 | 329,485 |
| 2025 | 328,560 |
Neighboring counties
- Grand County west · 16,496 people
- Larimer County north · 377,292 people
- Broomfield County southeast · 79,174 people
- Weld County northeast · 378,426 people
- Gilpin County southwest · 6,073 people
- Jefferson County south · 580,451 people
Printable Boulder County map
The PDF is a vector file with real text: it prints sharp on Letter paper and you can search it for a town. The PNG is 2400 pixels wide for slides and documents. Both are free to use with a credit to WhichCounty.
- PDF (Letter) (94 KB)
- PNG (2400 px) (73 KB)
Paste this code to embed the map on your site:
Sources
- Boundaries: U.S. Census Bureau, 2025 Cartographic Boundary Files (1:500,000).
- Population: Census Bureau county and city estimates, Vintage 2025. CDP populations: American Community Survey 2020–2024.
- Places and ZIP codes: Census Bureau 2026 Gazetteer and 2020 ZIP Code Tabulation Area relationship files.
- County seat, founding year and name origin: Wikidata (CC0), checked against state sources.
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