The United States' largest energy producer, Texas, pumped an estimated 2.75 million barrels of oil per day in February -- the most since 1980, showed a petroleum index released Wednesday. February crude production in the Lone Star state reached an estimated 77.2 million barrels -- up 22.4 percent from the same period last year, according to the Texas Petro Index, a composite index based on a comprehensive group of upstream economic indicators released by the Texas Alliance of Energy Producers, the nation's largest state association of independent oil and gas producers. The estimated Texas natural gas output was more than 625.2 billion cubic feet in February, up about 1 percent year on year. Karr Ingham, the economist who created the index, said higher wellhead prices caused an even more dramatic increase in the value of oil and gas produced in February, which rose by more than 2.85 billion dollars from the previous year to 10.63 billion dollars. Texas produced almost 35 percent of the country's crude oil in 2013, three times more than any other state, the U.S. Energy Information Administration (EIA) said last month. The second largest state producer was North Dakota with 12 percent of U.S. crude oil production, followed by California and Alaska at close to 7 percent each and Oklahoma at 4 percent. The federal offshore Gulf of Mexico produced 17 percent. U.S. crude oil production boomed in 2013, growing 15 percent to 7.4 million barrels per day, according to the EIA. Texas and North Dakota both saw their own oil production grow by 29 percent last year from 2012 levels. Crude oil is produced in 31 U.S. states and two offshore federal regions -- the Gulf of Mexico and the Pacific Coast. Of those 33 producing areas, 10 supply more than 90 percent of the U. S. output.