Offshore oil and gas in the United States provides a large portion of the nation’s oil and gas supply. Large oil and gas reservoirs are found under the sea offshore from Louisiana, Texas, California, and Alaska. Environmental concerns have prevented or restricted offshore drilling in some areas, and the issue has been hotly debated at the local and national levels. Production From 1954 to 2007, federal offshore tracts produced of oil and of natural gas. In 2007, federal offshore tracts produced 27% of the oil and 14% of the natural gas in the United States. Three of the top ten oil fields in the United States in terms of the proven remaining reserves were offshore in the Gulf of Mexico in 2007 (Mars-Ursa, Thunder Horse, and Atlantis). The oil production in the offshore area owned by the federal government reached in 2007, down from the record of produced in 2002. 2.86 TCF of offshore gas produced in 2007 was down from the high of 5.25 TCF produced in 1996. Ownership of offshore oil and gas The issue of state versus federal ownership has a long and contentious history (see Tidelands). The US Supreme Court ruled in 1947 that the federal government owned all the seabed off the California coast; the court applied the same doctrine against Louisiana and Texas in 1950. The court ruling invalidated existing state leases over producing offshore oil fields in the three states. However, the US Congress passed the Submerged Land Act in 1953, which recognized state ownership of the seabed within of the shore. That same year Congress also passed the Outer Continental Shelf Act, which gave the federal government jurisdiction over minerals on and under the seabed farther offshore from state waters. The first federal offshore lease sale was held in 1954, to offer oil production rights under federal seabed in offshore Louisiana. State ownership Each coastal state owns the territory extending from the shore at mean low tide, and has jurisdiction to decide whether or not, and under what terms, to lease the territory for oil and gas. Exceptions include Texas and the west coast of Florida, which for historical reasons own the seabed out to from the shore. Louisiana is included in the 3 nautical mile rule, but because it had active offshore leases defined before 1950 (and before most other states), its territory is measured using the Admiralty Nautical Mile, while