- With a 2010 population of 7,265, Clarkston is the urban center, though not the county seat, of tiny Asotin County in the southeast corner of Washington. At the confluence of the Snake and Clearwater rivers, it is a twin town with Lewiston, Idaho, just across the Snake River. In 1896 the Lewiston-Clarkston Improvement Company, an irrigation and hydro-electric venture, founded and laid out Clarkston, one of the few early examples of urban planning in the Pacific Northwest. Lewiston has always been the older, larger, and more industrial of the two towns, which since 1899 have been linked by a series of bridges over the Snake River. Although rivals in some respects, the two cities see their interests as mutually connected and in fact maintain a joint Chamber of Commerce. The final dams on the Columbia and Snake rivers provided enough slack water to enable commercial shipping to both cities. Clarkston, the easternmost port in Washington, bustles with huge wheat barges, trains, trucks, and river cruise ships.