OK, everybody listen up!
I'm not sure when 8-9-10 block clusters, and their correspondingly narrow chains came into being. They may be off topic on Dale's list, but I guaranty they're off topic on mine.
As Harvey has said, some of the earliest derailleurs were set up to run 1/2X1/8 chain, but for the most part, the classic derailleurs we are concerned with are set up for 1/2X3/32.
The fun stuff comes in when you consider track chain. Up to the early 60's 1X3/16 block chain was considered the accepted norm for track bikes. "Back in the day..." roller chain was considered too weak for track riding, especially the match sprint. When he came out of retirement to capture the British Championship, Reg Harris (age 54) said, I have full confidence in the new cotterless cranks, but a sprinter must use block chain!"
Harvey was also right that it was the loss of every other gear ratio that led to the move away from block chain. Dave Staub once told me of he and his partner riding a Jack Taylor tandem at the Olympic trials, (back when the Olympics still included a tandem match sprint) they had two rear cogs, an 8 and a 7. With the 8, they "ran out of gear" and their opponents would come by in the last few meters. With the 7, they were still winding out, and gaining on their opponents, when they ran out of race track. Obviously pretty frustrating. The perceived advantage of using block chain was that there was no stretching of the chain, when you got out of the saddle and stomped on the pedals the bike reacted instantly.
I would imagine that increases in metallurgy also made 1/2X1/8 chain perform more like block chain, and eased the transition.
BTW, in Catalogo N. 14, Campagnolo offers both chainwheels and cogs in 1X1/8. Now there's a real rarity! Ted Ernst verified my theory that 1X1/8 block chain was used by pursuiters and kilo riders because their type of racing did not require the explosive acceleration of the match sprints.
Bill (inchpitch) Curtis
Costa Mesa, CA