- One of the original counties of Washington Territory, Cowlitz County occupies the lower portion of the Cowlitz River and part of Washington’s shore of the Columbia River. One of the early conventions to form Washington Territory met at Monticello, which later became Longview. Logging and milling have historically been the big part of the county’s economy until the latter part of the twentieth century. A lumber mill led directly to the planned community of Longview, named after lumberman Robert A. Long (1850-1934).