The data, like regulations, of gas stations and their underground petroleum storage tanks is spread across many regional data sets.
The EPA has a nationwide tool called Underground Storage Tank (UST) Finder that shows every UST and Leaking UST site in the country. Although the data is not live and may be several years out of date. The tool also provides summary data by County.
Some states track their own UST and LUST data. If you would like to see your state added please email firstname.lastname@example.org.