Washington County was originally formed in 1838 as Slaughter County in honor of William B. Slaughter, the secretary of Wisconsin Territory. The county, still named Slaughter County, became part of Iowa Territory on July 4, 1838 when it was organized. To honor George Washington, the county opted to change its name on January 25, 1839. The first settlers arrived in Washington County in 1835. The homesteads did not start until 1836. A town, Astoria, was built in the present township of Oregon; it became the first county seat and housed the first court house. The county seat was moved to the city of Washington in 1839. The first religious society, organized by Reverend J.L. Kirkpatrick, a Methodist minister was created in 1839. The first newspaper was established in 1853; it was published for two years. In 1856 another newspaper started up; it has continued to the present. The major waterways through Washington County are the Skunk and English Rivers, and Crooked Creek. Timber is found in abundance around these waterways, which has allowed a timber industry to grow up. In 1855 Washington hosted the county's first bank. The county population swelled after 1858, when a railway line belonging to the Mississippi and Missouri Railroad was laid there.
Geography
According to the U.S. Census Bureau, the county has a total area of, of which is land and is water.
The 2010 census recorded a population of 21,704 in the county, with a population density of. There were 9,516 housing units, of which 8,741 were occupied.
2000 census
As of the census of 2000, there were 20,670 people, 8,056 households, and 5,631 families residing in the county. The population density was. There were 8,543 housing units at an average density of. The racial makeup of the county was 97.04% White, 0.29% Black or African American, 0.19% Native American, 0.25% Asian, 0.03% Pacific Islander, 1.51% from other races, and 0.68% from two or more races. 2.73% of the population were Hispanic or Latino of any race. There were 8,056 households out of which 31.40% had children under the age of 18 living with them, 60.30% were married couplesliving together, 6.70% had a female householder with no husband present, and 30.10% were non-families. 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. The average household size was 2.50 and the average family size was 3.04. In the county, the population was spread out with 26.10% under the age of 18, 7.00% from 18 to 24, 26.80% from 25 to 44, 22.30% from 45 to 64, and 17.90% who were 65 years of age or older. The median age was 39 years. For every 100 females, there were 93.00 males. For every 100 females age 18 and over, there were 90.10 males. The median income for a household in the county was $39,103, and the median income for a family was $45,636. Males had a median income of $29,592 versus $22,818 for females. The per capita income for the county was $18,221. About 5.10% of families and 7.60% of the population were below the poverty line, including 10.30% of those under age 18 and 7.30% of those age 65 or over.
