If you're a bargain-hunter you may not be able to resist a trip to Oklahoma City, OK. There you'll find the OnCue Express selling gas at $1.99 per gal. That's the first gas station in the U.S. to sell gas below $2 per gallon since July 30, 2010.

“We knew when we saw crude oil prices drop last week that we'd break the $2 threshold pretty soon, but we didn't know if it would happen in South Carolina, Texas, Missouri or Oklahoma,” said Patrick DeHaan, senior petroleum analyst for GasBuddy. “Those are all low-tax states and all have statewide averages at $2.52 or less.

“Today's national average, $2.74, now makes the current price we pay a whopping 51 cents per gallon less than what we paid a year ago, and 24 states are seeing even greater differences between today's and year-ago prices,” he added.

Florida leads that group with a 69.5 cent difference between today's average and that of one year ago.

Missouri has the lowest state average in the country at $2.43 today.