The Cahaba River. It is the natural habitat of the Cahaba lily, an endangered species of water lily.
Mississippi has the longest border with Alabama.
The longest highway in Alabama is Interstate 65. It stretches from the border with Tennessee almost to the border of Florida. Given that it is almost border to border, this would make it the longest one in the state.
The state of Mississippi is the 32nd largest of the US states. (The Mississippi River is the longest single river in the US. The Jefferson-Missouri-Lower Mississippi combination is the longest combined flowing river, 4th longest in the world, although much of the western Missouri is not navigable.)
The Des Moines River is the largest river flowing across the state of Iowa. The major rivers in Iowa are Cedar River, Des Moines River, Iowa River, Mississippi River, and Missouri River.
alabama
The Mississippi River is west of the state Alabama
The St Johns River is 310 miles long making it the longest river in the state of Florida.
The Willamette River is the longest river "in" the State of Oregon. The Columbia and Snake are both much longer but are not completely "in" the State of Oregon.
hudson river
Mississippi
Duck River (Tennessee) The Duck River is the longest river located entirely within the U.S. state of Tennessee.
The Colorado River is the longest river in the state of Arizona. The Colorado River flows through the Grand Canyon.