The Chicot aquifer system underlies an area of approximately 9,500 mi2 in southwestern Louisiana and is located within the Gulf Coastal Plain physiographic province. The region includes all or parts of 15 parishes -- Vernon, Rapides, Evangeline, Allen, Beauregard, Calcasieu, Jefferson Davis, Acadia, St. Landry, Lafayette, St. Martin, Cameron, Iberia, Vermilion, and St. Mary. The Chicot aquifer system is a major source of groundwater for southwestern Louisiana, accounts for approximately 48 percent of all groundwater use in the State, and provides freshwater for public supply, industry, agriculture, and aquaculture (Collier and Sargent, 2018). Withdrawals of groundwater have created water-level gradients favorable for saltwater encroachment, and future water availability and production in the region could be impacted by poor water quality. This product is part of a larger study of the Chicot aquifer system in southwestern Louisiana that will benefit local, State, other Federal cooperators, and stakeholders. The extent given here represents the geographic extent of the Chicot aquifer system in southwestern Louisiana and was created using elevation information from U.S. Geological Survey digital elevation models, surface geology maps, and previously published extents (Lovelace and others, 2004; Casarez, 2020).