The U.S. Geological Survey said there were 32 billion barrels of technically recoverable crude oil in the country.
The USGS estimates there are 32 billion barrels of oil, 291 trillion cubic feet of natural gas and 10 billion barrels of natural gas liquids in mean potential undiscovered reserves.
The estimates don't include federal offshore areas.
"By providing geologically based, domestically consistent estimates of the potential additions of oil and gas from the growth in reserves in known fields, and placing that information in the public domain, we are furnishing a valuable projection on how much and where fossil fuels may be produced in the future," USGS Director Marcia McNutt said in a statement.
Energy policy in the United States has taken center stage during the presidential election year. Critics of U.S. President Barack Obama's policies say he's blocking access to vast deposits of oil and natural gas. The administration notes that domestic production is at historic highs.
The Energy Department's Energy Information Administration reports that proven oil reserves in the United States increased 13 percent in 2010 to 25.2 billion barrels. Proven natural gas reserves passed 300 tcf for the first time in U.S. history in 2010 to reach 317.6 tcf.