Once a course of the Mississippi River, Bayou Lafourche is a 106-mile waterway from Donaldsonville to the Gulf of Mexico that helped shape Louisiana's coastline by carrying fresh water, sediment, and nutrients southward. About 800 to 2,500 years ago it was the Mississippi riverbed, and after the river carved a different route to the Gulf, Bayou Lafourche became a distributary channel during high water. Originally called the Chetimachas River and La Fourche des Chetimaches, it was an important passageway for American Indians, principally the Chitimacha tribe. Donaldsonville emerged in 1750 at the confluence of the Mississippi River and Bayou Lafourche as an important trading post and one of the oldest settlements in the state. Along with Bayou Maringuoin, Bayou Teche, and other relict channels and distributaries of the Mississippi, Bayou Lafourche helped form a coastal landscape of bayous, bays, lakes, and marshes left behind as the river's main flow shifted. Historically, the Mississippi River and Bayou Lafourche helped counteract subsidence in the area, but frequent overflows became too burdensome for residents under early laws that made landowners responsible for flood prevention. In 1903 the U.S. Army Corps of Engineers built a high levee at the junction of the two waterways to separate them and prevent flooding. Water quality later suffered from the lack of seasonal fresh-water flow and from increased agricultural and industrial commerce in the Lafourche watershed. In the 1950s the Mississippi was partially reconnected to Bayou Lafourche by a pumping station that restored fresh water flow, and community efforts continue to address water supply, coastal restoration, adequate flow, and recreation.