Spokane County is a county in the state of Washington, United States. Its population was 471,221 as of the 2010 census, making it Washington’s fourth-most populated county. Spokane, the state’s second biggest city after Seattle, is the largest city and county seat. The Spokane tribe inspired the county’s name.

Spokane County is part of the Spokane-Spokane Valley metropolitan statistical area, which is also part of the larger Spokane-Coeur d’Alene combined statistical region, which includes neighboring Kootenai County, Idaho.

The county has a total area of 1,781 square miles (4,610 km2), of which 17 square miles (44 km2) (0.9 percent) are covered by water, according to the United States Census Bureau. The Spokane River beyond Long Lake Dam (the county line of Stevens County) is the lowest point in the county, at 1538 feet (468 metres) above sea level. (Within Riverside State Park, there is virtually little elevation difference between the dam and the mouth of the Little Spokane River.) Mount Spokane’s peak, at 5,887 feet, is the county’s highest point (1,794 m).

Spokane County has a diverse geologic history and geography. The arid terrain of the Columbia Basin to the west, and the foothills of the Rockies—the Coeur d’Alene Mountains, which rise to the east in northern Idaho—to the east. Spokane County is located in a transition zone between the basaltic Channeled Scablands steppe plains to the west and the steep, timbered Rocky Mountain foothills to the east. The area has evidence of past geologic events that influenced the area and region, such as the Missoula Floods, which occurred 12,000 to 15,000 years ago.

The Saltese Flats and Saltese Uplands, to the southeast, are characterised by a shrub–steppe environment with grassy slopes and ravines. The county is also in a transition zone in terms of ecology, roughly divided between the Columbia Plateau ecoregion in the southwest, where it is at the eastern edge of the basaltic Channeled Scablands steppe plain, and the Northern Rockies ecoregion in the northwest, which is the rugged and forested Selkirk Mountains.

The county has a total area of 1,781 square miles (4,610 km2), of which 17 square miles (44 km2) (0.9 percent) are covered by water, according to the United States Census Bureau. The Spokane River beyond Long Lake Dam (the county line of Stevens County) is the lowest point in the county, at 1538 feet (468 metres) above sea level. (Within Riverside State Park, there is virtually little elevation difference between the dam and the mouth of the Little Spokane River.) Mount Spokane’s peak, at 5,887 feet, is the county’s highest point (1,794 m).

Spokane County has a diverse geologic history and geography. The arid terrain of the Columbia Basin to the west, and the foothills of the Rockies—the Coeur d’Alene Mountains, which rise to the east in northern Idaho—to the east. Spokane County is located in a transition zone between the basaltic Channeled Scablands steppe plains to the west and the steep, timbered Rocky Mountain foothills to the east. The area has evidence of past geologic events that influenced the area and region, such as the Missoula Floods, which occurred 12,000 to 15,000 years ago. The Saltese Flats and Saltese Uplands, to the southeast, are characterised by a shrub–steppe environment with grassy slopes and ravines.

The county is also in a transition zone in terms of ecology, roughly divided between the Columbia Plateau ecoregion in the southwest, where it is at the eastern edge of the basaltic Channeled Scablands steppe plain, and the Northern Rockies ecoregion in the northwest, which is the rugged and forested Selkirk Mountains.

The county has 471,221 people, 187,167 households, and 118,212 families according to the 2010 United States Census.

The population density was 267.2 people per square mile (103.2 people per square kilometre). The average density of the 201,434 dwelling units was 114.2/sq mi (44.1/km2). The county was 89.2 percent White, 2.1 percent Asian, 1.7 percent African American, 1.5 percent American Indian, 0.4 percent Pacific Islander, 1.2 percent other races, and 3.8 percent mixed race.

30.9 percent of the 187,167 homes had children under the age of 18, 47.2 percent were married couples living together, 11.2 percent had a female householder without a husband present, and 36.8 percent were not families; 28.6 percent of the households were made up of individuals. The average family size was 2.44 people, while the average household size was 2.44 people. The average age was 36.8 years old.

The county’s typical household income was $47,250, while the median family income was $59,999. Males had a median income of $44,000, while females had a median income of $33,878. The county’s per capita income was $25,127. Around 9.1 percent of households and 14.1 percent of the population were poor, including 17.0 percent of those under the age of 18 and 8.5 percent of those 65 and over.