In 2019, the top six primary energy—producing states—Texas, Pennsylvania, Wyoming, Oklahoma, West Virginia, and North Dakota—accounted for 55 quadrillion British thermal units (quads), or 55% of all of the primary energy produced in the United States. In 2000, these six states had accounted for 39% of the nation’s primary energy production, indicating that primary energy production has become more concentrated to the top producing states.