Recently I had the chance to play an 1899 Steinway that was in a retreat center. It appeared to be around 6 feet long, and was in pretty good condition considering the age (I don't know what work has been done on it)... the curious thing to me was that the keys - especially the black one - seemed a little shorter than today's pianos. Is this typical of older pianos?

No,An 1899 Steinway in the 6' range was most likely an AII which would have been 6'2". The sharps are not really considered short to modern standards. Now I have seen some AI which was the earliest A scale 1878-1896ish where the sharps were a bit stubby or shorter. The later duo-art players XR and OR definitely had both shorter naturals and sharps.