Breton Wilderness Area consists of 5,000 + acres on Breton Island, part of the Chandeleur Barrier Island chain located off the Mississippi River Delta of southern Louisiana. Ground cover is low sandy beaches on the Gulf of Mexico side, falling off on the mainland side into ponds, inlets, and salt-water marshes. The IMPROVE site representing Breton Wilderness Area is BRET1, located at the southeastern extreme of the Mississippi Delta, about 80 km (50 mi) south-southwest of the Wilderness, with Gulf Coast waters between.