Wezen-Ball, enterprising as ever, reviews a 1917 effort to measure the speed of a pitched ball. Money quote:

The Popular Science article is called "Two and a Half Miles a Minute: That's the speed at which a pitched ball travels." That's 150 mph. We won't be reaching those speeds any time soon. There might have been significant measurement and calculation error in that study, but it's still fascinating to see what people were doing nearly 100 year ago to better understand the game of baseball. We should just be thankful that we no longer have to resort to such elaborate means to get that kind of data. Instead, we just spend hours and hours analyzing it. Maybe we haven't changed all that much. Not that I'm complaining...

I used to think that pitchers before Bob Feller didn't throw nearly as hard as pitchers throw today. I thought that even the top power pitchers of the 1920s and '30s -- again, before Feller -- topped out around 90 miles an hour. If only because most of the film I've seen of pitchers from that era just don't suggest that much effort was being expended.
Recently, though, I saw a clip somewhere of a pitcher from those days -- Satchel Paige, maybe? -- and his pitching motion was practically indistinguishable from the pitching motions we see today.

No, pitchers didn't throw 150 miles an hour. I don't believe they threw, on average, as hard as pitchers throw today. Because 1) they weren't asked to max out, and 2) everyone in every sport is stronger and faster, more dynamic today than yesterday; why would pitchers be any different?

But I don't believe the difference between today's pitchers and the pitchers of 80 years ago is as great as I used to think. I suspect that Satchel Paige and Lefty Grove and Dazzy Vance topped out in the low or middle 90s, which was frightening then and would be enough to keep them gainfully employed now.