The state of South Carolina has the cheapest average gas prices in the United States as of October 2015. CNN Money pegs the average per gallon gas price in South Carolina at $1.96, while GasBuddy estimates the state's average price to be $1.93 based on slightly newer data.
Other states that also have per-gallon prices lower than $2 as of October 2015 include New Jersey, Mississippi, Alabama, Louisiana and Tennessee. Historically, states in the American southeast have been joined by New Jersey in having the nation's lowest overall taxation rates on fuel, which contributes to lower gasoline prices. The American Automobile Association releases a Fuel Gauge Report each month that is a comprehensive source of information about national gas prices.