Alabama River A river formed in central Alabama north of Montgomery by the confluence of the Coosa and Tallapoosa Rivers and flowing about 510 km (315 mi) southwest to join the Tombigbee River.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.