When I worked at "Oscar's Flying A" gas station back in 1965/66 before I joined the Marine Corps, it was around a quarter ... it was no joke then when somebody'd drive in and say, "A dollar's worth of your finest, please!"
(Best part of that job was that almost nightly, lonely Mrs. Madsen would take a drive, and start it off at the gas station....we kids loved to wash the windshield, over and over and over and over again - she was a flasher)
Ha! 19.9 cents, Columbia, Missouri, 1969. My all-time rock bottom price. Columbia had the first serve-yourself gas station that I ever ran across, too. It was called “U-Pump-Ethyl” — No kidding! I always wanted to meet Ethyl, but she never showed up.