Tieton is a city in Yakima County, Washington, United States. The population was 1,389 at the 2020 census. In recent years, Tieton ha…Tieton is a city in Yakima County, Washington, United States. The population was 1,389 at the 2020 census. In recent years, Tieton has suffered economic depression, with the decline of its fruit warehouses. As of 2007, a Seattle lawyer and the founding president of the art publishing house Marquand Books have been investing in the city and attempting to revive it, with a project they call project "Mighty Tieton."