Ala. Code § 41-2-3: Boundary Between Alabama and Florida - Generally.

The boundary line between Alabama and Florida is the line commonly known as the “mound line,” or “Ellicott’s Line,” as distinguished from a blazed line known as the “upper” or “Coffee Line,” commencing at a point on the Chattahoochee River, near a place known as “Irwin’s Mills”; and from thence to the Perdido River, marked the whole distance by blazes on the trees and by mounds of earth, at distances of about one mile.