Walla Walla County is a county located in the U.S. state of Washington. As of the 2020 census, its population was 62,584. The county seat and largest city is Walla Walla. The county was formed on April 25, 1854 and is named after the Walla Walla tribe of Native Americans.

Washington, officially the State of Washington, is a state in the Pacific Northwest region of the United States. It is often referred to as Washington state to distinguish it from the national capital, both named for George Washington. Washington borders the Pacific Ocean to the west, Oregon to the south, Idaho to the east, and the Canadian province of British Columbia to the north. The state was formed from the western part of the Washington Territory, which was ceded by the British Empire in the Oregon Treaty of 1846. It was admitted to the Union as the 42nd state in 1889. Olympia is the state capital, and the most populous city is Seattle.