Summit County was organized as one of the seventeen original Colorado counties by the First Territorial Legislature on November 1, 1861. It was named for the many mountain summits in the county. Until February 2, 1874, its boundaries included the area now comprising Summit County,Grand County,Routt County,Moffat County,Garfield County,Eagle County, andRio Blanco County.
In 1874, the northern half of the original Summit County was split off to formGrand County; with the creation ofGarfield andEagle counties in 1883, Summit County arrived at its present boundaries. In addition, Summit County has seen two major boom eras.
According to theU.S. Census Bureau, the county has a total area of 619 square miles (1,600 km2), of which 608 square miles (1,570 km2) is land and 11 square miles (28 km2) (1.8%) is water.[5]
The terrain of the county is mountainous with elevations ranging from 7,957 feet (2,425 m) atGreen Mountain Reservoir to 14,270 feet (4,350 m) atGrays Peak. The elevation of the county seat of Breckenridge is 9,602 feet (2,927 m), making it one of the highest cities in the state of Colorado and the United States.[6] Much of the county has analpine climate (ET in theKöppen Classification) characterized bytundra vegetation. Breckenridge and other similar elevations in the county have asubarctic climate (Dfc) characterized by cool summers and abundant snowfall in winter.
U.S. Decennial Census[8] 1790–1960[9] 1900–1990[10] 1990–2000[11] 2010–2020[1]
As of thecensus[12] of 2000, there were 23,548 people, 9,120 households, and 4,769 families residing in the county. Thepopulation density was 39 people per square mile (15 people/km2). There were 24,201 housing units at an average density of 40 per square mile (15/km2). The racial makeup of the county was 91.84%White, 0.68%Black orAfrican American, 0.48%Native American, 0.87%Asian, 0.07%Pacific Islander, 3.96% fromother races, and 2.10% from two or more races. 9.79% of the population wereHispanic orLatino of any race.
There were 9,120 households, out of which 24.00% had children under the age of 18 living with them, 44.00% weremarried couples living together, 4.40% had a female householder with no husband present, and 47.70% were non-families. 21.60% of all households were made up of individuals, and 1.60% had someone living alone who was 65 years of age or older. The average household size was 2.48 and the average family size was 2.86.
In the county, the population was spread out, with 17.40% under the age of 18, 15.70% from 18 to 24, 44.30% from 25 to 44, 19.40% from 45 to 64, and 3.30% who were 65 years of age or older. The median age was 31 years. As of 2014, the life expectancy in Summit County was 86.83 years, the longest average life expectancy of any county in the United States.[13] For every 100 females there were 139.00 males. For every 100 females age 18 and over, there were 144.90 males.
The median income for a household in the county was $56,587, and the median income for a family was $66,914 (these figures had risen to $65,281 and $80,441 respectively as of a 2007 estimate). Males had a median income of $33,741 versus $27,017 for females. Theper capita income for the county was $28,676. About 3.10% of families and 9.00% of the population were below thepoverty line, including 4.30% of those under age 18 and 3.40% of those age 65 or over.
The 2019 average real estate prices in Summit County were $1,262,929 for a single family home, $559,776 for a condo, townhome or duplex and $344,945 for a vacant piece of land (YTD through December 2019).[14]
According to a report in theJournal of the American Medical Association, residents of Summit County had a 2014 life expectancy from birth of 86.83 years in 2014, the longest in the United States.[15] Both men and women live longer in Summit County than in any other county in the United States: 85.5 years for men and 88.0 years for women is the life expectancy at birth.[16] Two contiguous counties,Pitkin andEagle counties, rank numbers two and three in the nation in life expectancy. Factors contributing to the high life expectancy in Summit County are "high education, high income, high access to medical care, the people are physically active, obesity is lower than anywhere else — so you’re doing it right,” said Dr. Ali Mokdad, one of the study's co-authors.[17]
Summit County is liberal in most elections. Since 1988 the county has trended strongly toward theDemocratic Party, like many other counties in Colorado dominated by ski towns. In 2020, Joe Biden's performance was the best by a Democrat since 1916, and Kamala Harris' performance was only slightly worse in 2024.
United States presidential election results for Summit County, Colorado[18]
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