Apalachicola River, a river in Florida. It begins at the junction of the Chattahoochee and Flint rivers on the Georgia-Florida border, where Lake Seminole is formed by Woodruff Dam. From there the Apalachicola flows generally southward for about 90 miles (145 km) through northwestern Florida and empties into Apalachicola Bay, an arm of the Gulf of Mexico. The river's extreme southern end is part of the Intracoastal Waterway. The Apalachicola and Chattahoochee form a 500-mile (800-km) river system navigable by barge to Columbus, Georgia.