Sedgwick County is the northeasternmost of the 64 counties in the U.S. state of Colorado. As of the 2010 census, the population was 2,379. The county seat is Julesburg. The county was named for Fort Sedgwick, a military post along the Platte Trail, which was named for General John Sedgwick.
According to the U.S. Census Bureau, the county has a total area of 549 square miles (1,420 km), of which 548 square miles (1,420 km) is land and 1.4 square miles (3.6 km) (0.2%) is water.
As of the census of 2000, there were 2,747 people, 1,165 households, and 802 families residing in the county. The population density was 5 people per square mile (2/km²). There were 1,387 housing units at an average density of 2 per square mile (1/km²). The racial makeup of the county was 90.50% White, 0.51% Black or African American, 0.15% Native American, 0.76% Asian, 0.07% Pacific Islander, 5.97% from other races, and 2.04% from two or more races. 11.43% of the population were Hispanic or Latino of any race.
There were 1,165 households out of which 26.40% had children under the age of 18 living with them, 59.10% were married couples living together, 6.60% had a female householder with no husband present, and 31.10% were non-families. 29.40% of all households were made up of individuals and 13.60% had someone living alone who was 65 years of age or older. The average household size was 2.31 and the average family size was 2.83.
In the county, the population was spread out with 22.80% under the age of 18, 6.60% from 18 to 24, 23.50% from 25 to 44, 25.00% from 45 to 64, and 22.10% who were 65 years of age or older. The median age was 43 years. For every 100 females there were 100.10 males. For every 100 females age 18 and over, there were 97.20 males.
The median income for a household in the county was $28,278, and the median income for a family was $33,953. Males had a median income of $25,463 versus $16,392 for females. The per capita income for the county was $16,125. About 7.80% of families and 10.00% of the population were below the poverty line, including 13.70% of those under age 18 and 4.20% of those age 65 or over.