NEW YORK (CNNMoney.com) -- Gasoline prices - already below the $2- a-gallon mark - dropped for the 68th straight day in a national survey Monday.

The national average fell 2.1 cents to $1.908 per gallon of regular gasoline, according to the daily survey conducted for AAA, a motorist group. Over the last 68 days gas prices have decreased $1.947, or 50.5%.

The last time the national average for a gallon was near the current price was Feb. 25, 2005, when the national average was $1.902.

The price of gas is 53.6% off the record-high $4.114 per gallon reached in mid-July. Prices were down more than $1.17 per gallon from a year ago and 82.7 cents from a month ago.

Prices at the pump have sunk below an average of $2 a gallon in 36 states. It was cheapest in Missouri, at an average of $1.592, according to AAA.

All 50 states and the District of Columbia have prices below $3 a gallon. The most expensive gas is in Alaska, at $2.865 per gallon, according to AAA.

The AAA figures, compiled by Oil Price Information Services, are state-wide averages based on credit card swipes at up to 100,000 service stations across the nation. These are state-wide averages, and individual drivers may see lower fuel prices in different areas of each state.