Where is the Oglala Aquifer located?

The Oglala Aquifer is located in the High Plains region of the United States, which includes parts of eight states: Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. It is the largest aquifer in the United States, covering an area of approximately 174,000 square miles (450,000 km²). The aquifer is composed of porous and permeable sandstone, limestone, and dolomite, and it stores an estimated 3,000 trillion gallons (11,000 cubic kilometers) of water.