The Boston Mountains are the source of several rivers and streams. They flow out from the mountains in all directions. The Boston mountains are the sources of the White River, the Buffalo River, the Kings River and War Eagle Creek. Other rivers and streams having their headwaters in the Boston Mountains include the Illinois River, the Mulberry River, Lee Creek, Frog Bayou, Big Piney Creek, Illinois Bayou, and the Little Red River. To the south, the Arkansas River valley separates the Boston Mountains from the Ouachita Mountains.