Coordinates: 36°44′50″N 95°58′50″W / 36.747206°N 95.980597°W / 36.747206; -95.980597
According to the U.S. Census Bureau, the county has a total area of 424 square miles (1,100 km), of which 415 square miles (1,070 km) is land and 8.8 square miles (23 km) (2.1%) is water. It is the second-smallest county in Oklahoma by land area and smallest by total area. It lies in the Eastern Lowlands physiographic region, and is drained by the Caney River. Lakes and reservoirs include Copan Lake, Silver Lake and Bar-Dew Lake.
As of the 2010 United States Census, there were 50,976 people, 21,036 households, and 14,123 families residing in the county. The population density was 45/km² (118/mi²). There were 23,451 housing units at an average density of 55.3 per square mile (21.4/km²). The racial makeup of the county was 93.9% white, 2.4% black or African American, 10.3% Native American, 1.1% Asian, less than 0.1% Pacific Islander, 1.7% from other races, and 6.1% from two or more races. Five percent of the population were Hispanic or Latino of any race.
There were 21,036 households, out of which 30.1% had children under the age of 18 living with them, 52.1% were married couples living together, 11% had a female householder with no husband present, 4% had a male householder with no husband present, and 32.9% were non-families. Individuals living alone accounted for 28.7% of households and individuals who were 65 years of age or older living alone accounted for 12.9%. The average household size was 2.39 and the average family size was 2.91.
In the county, the population was spread out with 23.4% under the age of 18, 8.1% from 18 to 24, 22.8% from 25 to 44, 27.9% from 45 to 64, and 17.8% who were 65 years of age or older. The median age was 41.4 years. For every 100 females, there were 93.7 males. For every 100 females age 18 and over, there were 109.8 males.
The median income for a household in the county was $35,816, and the median income for a family was $43,514. Males had a median income of $34,201 versus $22,389 for females. The per capita income for the county was $20,250. About 8.70% of families and 11.90% of the population were below the poverty line, including 15.70% of those under age 18 and 7.80% of those age 65 or over.
Washington County Oklahoma neighborhoods include: Bison Road, Circle Mountain, Colonial Estates, Covington Park, Downtown Bartlesville, Eastland, E of S. Madison Blvd, Forest Creek, Glynnwood, Grand Prairie, Guinn Ln, Hillcrest Heights, Hogshooter, Jane Phillips MC, Jefferson, Katherine/De Bell Ave, Kenilworth, Legacy Estates, Macklyn Ln, Memorial Park, N. Spruce, Oak Park, Oglesby, Park Kiely, Parkland Manor, Pennington Hills, Quail Ridge, Rice Creek, Rolling Hills, Rolling Meadows, SE Washington Blvd, Silver Lake, Sooner Park West, Southeast Wilshire, Southern Hills Estates, South Madison, Southport, South Rogers, Stonewall Extended, Tuxedo, Village, Wayside, Westside Lupa, Woodland Park, Woodland View