[2] Washington County is included in the Iowa City Metropolitan Statistical Area.

To honor George Washington, the county opted to change its name on January 25, 1839.

[5][6] The first White American colonizers arrived in Washington County in 1835, and began establishing individual domiciles in 1836.

[8] The major waterways through Washington County are the Skunk and English Rivers, and Crooked Creek.

The county population swelled after 1858, when a railway line belonging to the Mississippi and Missouri Railroad was laid there.

[9] As of the census[16] of 2000, there were 20,670 people, 8,056 households, and 5,631 families residing in the county.

26.40% of all households were made up of individuals, and 12.50% had someone living alone who was 65 years of age or older.

[1] The county is served by 3 school districts[18] Highland Community School District includes:[19] The population ranking of the following table is based on the 2020 census of Washington County.