Colorado

Postal abbreviation CO. 645 ZIP codes across 64 counties.

Population5,862,189
Postal abbreviationCO
ZIP codes645 ZIP codes →
Area codes303719720748970983
Time zoneMountain
Counties64

Largest cities by population

Denver · 718,877Colorado Springs · 487,887Aurora · 394,432Fort Collins · 170,229Thornton · 144,187Arvada · 122,634Westminster · 115,484Pueblo · 111,561Greeley · 110,806Boulder · 106,433Longmont · 99,406Castle Rock · 79,123Loveland · 78,410Broomfield · 76,304Grand Junction · 68,142Commerce City · 66,445Parker · 61,783Littleton · 44,710Brighton · 42,059Windsor · 37,914Englewood · 34,129Erie · 33,808Wheat Ridge · 32,070Lafayette · 30,602Fountain · 29,300Evans · 22,396Montrose · 21,044Louisville · 20,786Golden · 20,417Clifton · 19,518

Largest counties by population

El Paso County · 742,999Denver County · 718,877Arapahoe County · 659,844Jefferson County · 579,377Adams County · 530,225Douglas County · 377,150Larimer County · 367,368Weld County · 350,396Boulder County · 328,961Pueblo County · 169,356

Counties in Colorado

Adams CountyAlamosa CountyArapahoe CountyArchuleta CountyBaca CountyBent CountyBoulder CountyBroomfield CountyChaffee CountyCheyenne CountyClear Creek CountyConejos CountyCostilla CountyCrowley CountyCuster CountyDelta CountyDenver CountyDolores CountyDouglas CountyEagle CountyEl Paso CountyElbert CountyFremont CountyGarfield CountyGilpin CountyGrand CountyGunnison CountyHinsdale CountyHuerfano CountyJackson CountyJefferson CountyKiowa CountyKit Carson CountyLa Plata CountyLake CountyLarimer CountyLas Animas CountyLincoln CountyLogan CountyMesa CountyMineral CountyMoffat CountyMontezuma CountyMontrose CountyMorgan CountyOtero CountyOuray CountyPark CountyPhillips CountyPitkin CountyProwers CountyPueblo CountyRio Blanco CountyRio Grande CountyRoutt CountySaguache CountySan Juan CountySan Miguel CountySedgwick CountySummit CountyTeller CountyWashington CountyWeld CountyYuma County

Population: U.S. Census Bureau, ACS 5-year estimates, 2024.