As of 2015, a good place to find state maps for gas prices is the Gas Buddy website. Prices can be obtained for most major cities and surrounding areas in the U.S.
The maps on gas Buddy also highlight areas of the U.S. by national gas price average. The site is updated often and is free to use.
Another good location for gas prices is the Gas Price Watch site. The site can locate gas prices by address, city or zip code. Users also have the ability to save searches for future reference. Gas Price Watch can look up prices for regular, midgrade, premium and diesel gas prices.