The area of today's Washington County was long inhabited by various indigenous people. In historic times, European traders encountered first Choctaw and later Creek Indians, who had moved southwest from Georgia as early European settlers encroached on their land.

Washington County was organized on June 4, 1800 from the Tombigbee District of the Mississippi Territory by proclamation of territorial governor Winthrop Sargent. It was the first county organized in what would later become Alabama, as settlers moved westward after the American Revolutionary War. Washington County is the site of St. Stephens, the first territorial capital of Alabama. In 1807 former U.S. Vice President Aaron Burr was arrested at Wakefield in Washington County, during his flight from being prosecuted for alleged treason (which he was eventually found innocent of).

Even though the U.S. government removed most of the Choctaw and Creek to Indian Territory (now Oklahoma) west of the Mississippi River in the 1830s, some Native Americans remained behind and became state (and U.S.) citizens. They struggled to maintain their Choctaw culture through years during which the U.S. government imposed a binary system of dividing people into white and "all other" people of color (blacks and Indians). In 1979 Alabama recognized the MOWA Band of Choctaw Indians. Its members are concentrated along the border of Mobile and Washington counties.
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Surrounding Counties: Mobile, Baldwin, Clarke & Choctaw  Mississippi: Jackson, George & Greene