No. Unleaded gasoline was available sporadically before the 1970s. The widespread availability began around 1975 when EPA regulations kicked in. The Clean Air Act amendments passed in 1970 called for improvements to automobile emissions, and as a consequence of that catalytic converters became widely adopted. Lead in exhaust rapidly fouls catalytic converters so those vehicles had to use only unleaded gasoline and, of course, unleaded gasoline had to be made available to the general public. After some back and forth it eventually worked out that 1975 was effectively the "launch year" for large numbers of cars with catalytic converters as well as widespread availability of unleaded gasoline (though, of course, many gas stations were providing unleaded gas prior to the 1975 "deadline"). And, in fact, in the state of California all US manufactured automobiles sold to consumers were mandated to have catalytic converters in 1975.

In general, it was possible to find unleaded gasoline at some gas stations across most of the country throughout the 20th century in the US. Starting in the early 1970s it became much more common, with a lot of gas companies offering low lead and unleaded gasoline in 1970 (for example, Texaco and Shell). In 1974 unleaded gasoline sales made up 5% of total gas sales, by 1976 it was up to about 20%, and by the early '80s unleaded gasoline started to overtake leaded gas.

Before 1923, gasoline did not contain tetraethyl lead. There had mostly been no need. The earlier gasoline engines had low compression. The ingenious Charles Kettering was aware that higher compression engines would be more efficient- the more the piston compressed the gas/air mixture, the greater would be the expansion of the hot gas on ignition, and the more power would be generated from the heat. But under high compression, gasoline would explode, or "knock". As higher-compression engines started to be developed ( especially in aircraft) after World War I , chemist Thomas Midgely in Kettering's GM laboratory in Dayton Ohio experimented with various different compounds, metal salts. Some of them were expensive, some corrosive, some immensely foul-smelling. Tetraethyl lead was found to work the best. In March 1923 GM sold the first leaded gasoline in Dayton Ohio. Soon the major automobile companies pooled their patents and it became widely available.

Interestingly, Kettering had thought high-compression engines would be necessary to keep the world from running out of oil. But GM decided it would gain more sales if it simply touted the extra power its higher-compression engines had, especially compared to the popular Ford Model T.

Thomas Midgely later also created Freon. Considering how much lead vapor went into into the air and CFC's into the ozone layer, for decades, Midgely probably had more effect on the earth's atmosphere than any other single human.

Alan P Loeb, Birth of the Kettering Doctrine: Fordism, Sloanism, and the Discovery of Tetraethyl Lead