NEW YORK (CNNMoney) -- Gas prices continued their nationwide decline on Tuesday, as South Carolina became the first state in nearly a year and a half to hit an average of less than $3 per gallon.
The statewide average price for South Carolina was $2.987 per gallon of unleaded gasoline on Tuesday, according to AAA. This is the first time that the statewide average in any state has dipped below $3 since Missouri crossed that line on Feb. 22, 2011.
"The last time South Carolina was below $3 a gallon was on Feb. 19, 2011," said AAA, in a prepared statement. "Protests in Libya began on Feb. 15, 2011, meaning it has taken a year and a half for prices to return to levels seen before the unrest in Libya began."
The national average for unleaded gasoline dropped to $3.397 per gallon, in its 14th consecutive decrease, according to the motorist group. That's the lowest price since Jan. 27, 2012, when the national average was $3.389. Gas has fallen by 10 cents in one week and by 25 cents in one month.
The ongoing plunge in gas prices is the result of an oversupply of light sweet crude oil, not only from West Africa, but also the United States, according to Tom Kloza, chief oil analyst for the Oil Price Information Service.
"U.S. domestic production in the lower 48 [states] is going gangbusters," he said. "It's booming."
Prices are also being pulled down by a lack of demand due to the lackluster economy. In one of the latest signs of this, a report released Tuesday showed that consumer confidence has fallen for four months straight.
Gas is particularly cheap in the Southeast, where prices in Mississippi, Alabama and Tennessee hover just above $3 a gallon. The region benefits from low taxes and close proximity to Gulf Coast refineries, according to AAA.
Gas is significantly more expensive in the Western states, where there are higher taxes and refinery disruptions, said AAA. In the non-contiguous states of Alaska and Hawaii, the statewide average price was still above $4 per gallon.
But despite the recent drops, the nationwide average for a gallon of gas is still up roughly 12 cents year-to-date, compared to $3.278 on Jan. 1.
Still, it's down more than 71 cents, or about 17%, from the all-time national high of $4.114 on July 17, 2008.