Interesting: the entry for the Apollo Guidance Computer (AGC) indicates it used integrated circuits—I had remembered hearing it used RTL (resistor-transistor logic).

It turns out both are true [1]. The "integrated circuits" were sort of "flat-packs" of RTL circuits. I had forgotten that early IC's were not quite what we envision today. Regardless I suppose ICs were RTL before they were TTL (before they were CMOS, etc.).

[1] https://en.wikipedia.org/wiki/Apollo_Guidance_Computer#Logic...

In particular, the IBM 1401 (two of them actually) that you can see demonstrated at the Computer History Museum in Mountain View are transistor-based and were very successful computers.

https://computerhistory.org/exhibits/ibm1401/

And before that with gears! (With limited success.)

I like how the 1937 "Model K" adder is literally on a breadboard.

(are those knife switches in the upper right?)