Washington County is a county located in the U.S. state of Nebraska. As of the 2010 census, the population was 20,234. Its county seat is Blair.
Washington County is included in the Omaha-Council Bluffs, NE-IA Metropolitan Statistical Area.
In the Nebraska license plate system, Washington County is represented by the prefix 29 (it had the twenty-ninth largest number of vehicles registered in the county when the license plate system was established in 1922).
Washington County is located in eastern Nebraska on the Missouri River. It was explored as early as 1739 by Pierre Antoine and Paul Mallet, who were on a trapping expedition to Canada. In 1804, Lewis and Clark reported the establishment of the new United States government to a council of Indian chiefs near the present site of Fort Calhoun. As a result of this Council, Fort Atkinson was established in 1819 and served as a key midwestern outpost until its abandonment in 1827.
The first permanent settlement in Washington County was made in 1854. In that same year, the county was organized as one of the eight original counties proclaimed by acting Governor Thomas B. Cuming. The county seat has been located in three different towns: Fort Calhoun, DeSoto, and finally at Blair, its present site since 1869.