<Tr> <Td> - min </Td> <Td> 0 cu ft / s (0 m / s) </Td> </Tr> <Tr> <Td_colspan="2"> Map of the Apalachicola River system with the Chattahoochee highlighted in dark blue . </Td> </Tr> <P> The Chattahoochee River forms the southern half of the Alabama and Georgia border, as well as a portion of the Florida border . It is a tributary of the Apalachicola River, a relatively short river formed by the confluence of the Chattahoochee and Flint rivers and emptying from Florida into Apalachicola Bay in the Gulf of Mexico . The Chattahoochee River is about 430 miles (690 km) long . The Chattahoochee, Flint, and Apalachicola rivers together make up the Apalachicola--Chattahoochee--Flint River Basin (ACF River Basin). The Chattahoochee makes up the largest part of the ACF's drainage basin . </P> <P> The source of the Chattahoochee River is located in Jacks Gap at the southeastern foot of Jacks Knob, in the very southeastern corner of Union County, in the southern Blue Ridge Mountains, a subrange of the Appalachian Mountains . The headwaters of the river flow south from ridges that form the Tennessee Valley Divide . The Appalachian Trail crosses the river's uppermost headwaters . The Chattahoochee's source and upper course lies within Chattahoochee National Forest . </P>

Which river forms the border between georgia and alabama