A very long time ago, 1970's. For a 1968 Pontiac GTO, I used single grade 40 and sometimes, 50 racing oil. I was a fool. I don't know if that oil was even detergent. Pennzoil or QS. I did switch to QS 10w40 for Winters.
I stuck with the 10w40 year-round for a long time. I had an episode in Jan. 1981 during an insane cold snap in the part of Pa. I was living in. It was anywhere from -25F to -32F every morning for approximately a week. Not super rare in a couple of notorious cold spots in Pa., but unheard of in that area. A Fiat 128 that I commuted in long distance, would start but the oil light would not go out. I quickly quit trying to do that. It must have been chilled window putty. Oil was QS 10w40. Too cold for that grade, but there was quickly an uproar to QS from numerous places. Turned out they owned it due to a bad batch of QS 10w40. Some, like me, got some bucks for an oil change. Others actually got engine replacements. I switched to 10w30 after that, even if that had no better winter specs. 20 years later, I got on the 5w30 bandwagon.