Mississippi's Big Sunflower River is the 2018 most endangered river in the United States. (American Rivers/John Ruskey) At a Glance The river advocacy group American Rivershas been rating U.S.rivers since 1984.Selections for theendangered list are primarily based on whether a major policy decisionis in the works about a river forthe coming year. A river advocacy group has announced its 10 most endangered rivers list for 2018. American Rivershas been rating the most endangered U.S.rivers since 1984 and releases to help...