Actually, apart from San Francisco, no, no they weren't. However talking about the Spanish Flu, the whole episode lasted two years and had 10 times more deaths in the same period. I guess sometimes we need to have perspective.
I don't know whether or not lockdowns would have saved any more lives a century ago or whether they would do what seems to be the case today and merely delayed those deaths. But what I do know is if they didn't let the virus rip, it would have been going on for far longer than two years and the weaken mutation may have never came about. Also are you aware the deadly variant of the Spanish flu was due to the isolation of the trenches. How ironic.
Well, the Spanish flu actually originated in Kansas and my understanding is that even those first cases were very virulent.
As for restrictions, SF wasn't the only city to implement those. They are very similar to what was done last year: