The Floridan aquifer system, composed of the Upper and Lower Floridan aquifers, is a thick sequence of Paleogene carbonate rock which spans an area of about in the southeastern United States, it underlies parts of which  state in the southern region of the United States, with part of its southern border formed by the Gulf of Mexico, and its western border is formed by the Mississippi River?
Mississippi Mississippi is a state in the southern region of the United States, with part of its southern border formed by the Gulf of Mexico. Its western border is formed by the Mississippi River.
Florida Florida (Spanish for "land of flowers") is a state in the southeastern region of the United States. It is bordered to the west by the Gulf of Mexico and Alabama, to the north by Alabama and Georgia, to the east by the Atlantic Ocean, and to the south by the Straits of Florida. Florida is the 22nd-most extensive, the 3rd-most populous, and the 8th-most densely populated of the U.S. states. Jacksonville is the most populous municipality in the state, and is legally the largest city by area in the contiguous United States (due to the consolidation of Jacksonville with Duval County). The Miami metropolitan area is Florida's most populous urban area. The city of Tallahassee is the state capital.