<P> Petroleum in the United States has been a major industry since shortly after the oil discovery in the Oil Creek area of Titusville, Pennsylvania in 1859 . The petroleum industry includes exploration for, production, processing (refining), transportation, and marketing of natural gas and petroleum products . As of 2008, the U.S. was the world's third - largest oil producer (after Saudi Arabia and Russia), producing 8.5 million barrels of oil and natural gas liquids per day . The leading oil - producing area in the United States in 2014 was Texas (3.17 million barrels (504,000 m) per day), followed by the federal zone of the Gulf of Mexico (1.40 million barrels (223,000 m) per day), followed by North Dakota (1.09 million barrels (173,000 m) per day) and California (0.50 million barrels (79,000 m) per day). </P> <P> In 2015, US production of crude oil rose to 9.48 million barrels per day, the highest annual rate since 1972, and an increase of 90% from the 2008 production of 5.00 million barrels per day . On a monthly basis, however, US production peaked in April 2015 at 9.63 million barrels per day, then declined due to lower oil prices to 8.74 million barrels per day in August 2016 . US Natural gas production achieved new record highs for each year from 2011 through 2014 . </P>

Where does most of the us oil come from