Duckriver

The Duck River, 284 miles long, is the longest river located entirely within the U.S. state of Tennessee. Free flowing for most of its length, the Duck River is home to over 50 species of freshwater mussels and 151 species of fish, making it the most biologically diverse river in North America.
  • Length: 284 miles (457 km)
Data from: en.wikipedia.org