The Chattahoochee River originates from mountain springs, primarily Chattahoochee Spring, in the Chattahoochee National Forest in Habersham County. It flows southwestward, being joined by the Soque River and Chestatee River, eventually passing from the mountains into the piedmont area and flowing through Atlanta. Continuing its course, it flows through western Georgia, eventually becoming part of West Point Lake in Troup County on the Georgia/Alabama border. From there it flows southward, forming the Georgia/Alabama border, through Columbus, Georgia, before finally emptying into Lake Seminole, along with the Flint River. From Lake Seminole, the Apalachicola River flows southward through the panhandle of Florida into the Gulf of Mexico. The Chattahoochee River is Georgia's longest, at 436 miles.