Sometime during/soon after 1971 I used a teletype style terminal to use shared mainframe capability (easily learned language like Basic), while working for Signal Oil & Gas Co.
I think the computer was owned by McDonnel Douglas, and was called “Mc-Auto” or something along that line. I think the machine was located in the Bay area.
McAuto was still around in the early 1980s. We used their mainframes to run commercial/industrial/institutional building energy modeling software that the Trane Company licensed, TRACE, TRane Air Conditioning Economic. Not too much later, PCs were able to run TRACE and TRACE-like programs, and using it on the mainframe went the way of the dodo, like many things.