http://www.georgiaencyclopedia.org/nge/Article.jsp?id=h-2834 Altamaha River], The New Georgia Encyclopedia Including its longest tributary (the Ocmulgee) in length calculations, as is standard USGS practice, its length of 470 miles places it seventh on the list of U.S. rivers entirely within one state, behind only four Alaskan rivers, the Sacramento-Pit River in California, and the Trinity River in Texas.