The national average was $3.41 per gallon, up from the $3.35 reported for Feb. 17, AAA said.
Montana had the lowest state average, $3.14, while California had the highest, $3.79, for the Lower 48.
A dozen states reported an average price higher than $3.50 per gallon. The national average price one month ago was $3.28, though Monday's average price is nearly 50 cents cheaper than the same time last year.
AAA said regional refineries are preparing for regular seasonal maintenance, which is expected to lead to higher gasoline prices. The auto club said it may be April before drivers see prices start to decline.
The American Petroleum Institute said last week demand for gasoline in January was 1.1 percent higher than the same time in 2013, but 5.2 percent lower when compared with December.
A harsh winter for states east of the Mississippi River was credited with lower gasoline demand as many drivers were forced to stay home.