The Port Allen Lock connects the Mississippi River to the Gulf Intracoastal Waterway, shortening the distance to the Gulf of Mexico by approximately . The Lock, a free-floating structure, is the largest of its kind. It serves as a man-made break in the levee. The massive structure has 90-ton doors and sides. The lock was constructed in 1961 by the U.S. Army Corps of Engineers to replace the historic Plaquemine Lock. The Intracoastal Waterway is an east–west inland waterway shortcut that connects Florida and Texas, eliminating of shipping distance.