Head of Passes is the branching point near the Gulf of Mexico where the Mississippi River divides into Southwest Pass, South Pass, and Pass A Loutre, and it is generally regarded as the river’s mouth within the Bird’s Foot Delta. It has long been important for navigation, as the U.S. Army Corps of Engineers maintains a deep-water shipping channel from Southwest Pass upriver to Baton Rouge. During the Civil War, a Union blockade was established here in 1861 under the Anaconda Plan, leading to the Battle of the Head of Passes, in which the blockading force was temporarily driven off. It also serves as the reference point for measuring distances along the Lower Mississippi.