Lewiston is a city in and the county seat of Nez Perce County, Idaho, United States. It is the second-largest city in the northern Idaho region, behind Coeur d'Alene. Lewiston is the principal city of the Lewiston, ID - Clarkston, WA Metropolitan Statistical Area, which includes all of Nez Perce County and Asotin County, Washington. As of the 2000 census the population of Lewiston was 30,904 . The lowest point in the state of Idaho is located on the Snake River in Lewiston, where it flows out of Idaho and into Washington.