What happened to gasoline in the mid 1970s?

i pumped gas in the mid 80s we still had leaded then i think that was 86. I don't remember the octane. I do remember Sunoco ultra 94 was the chit in unleaded.

I remember guys with older cars "mixing" the leaded ...half tank of that with a half of Ultra 94.

what i can tell you obviously is leaded gas got phased out. I still see some signs in farm country that they sell leaded, but i do not know if it is the same as the old days.