Department of the Gulf north. On November 3, 1863, the northern boundary was extended to latitude 33° north. On July 25, 1863, the department/district was transferred to the Department of Mississippi and Eastern Louisiana. It remained in that department only until January 28, 1864, when it was transferred to the Department of Alabama and Eastern Mississippi. Upon being transferred, the department/district boundaries were redefined as beginning at the mouth of the Pearl River, running north to latitude 32° north, east to the Georgia State line and south to the Gulf of Mexico. On May 8, 1864, the boundary was again modified to define the
Gulf of Mexico shallow continental shelf waters. The basin contains a volume of roughly 2,500 quadrillion liters (550 quadrillion Imperial gallons, 660 quadrillion US gallons, 2.5 million km or 600,000 cu mi). The Gulf of Mexico is one of the most important offshore petroleum production regions in the world, comprising one-sixth of the United States' total production. The International Hydrographic Organization defines the southeast limit of the Gulf of Mexico as follows: A line leaving Cape Catoche Light () with the Light on Cape San Antonio in Cuba, through this island to the meridian of 83°W and to the Northward along this meridian