In case you're wondering (as I was):

Node 1: UCLA (30 August, hooked up 2 September, 1969) - SDS SIGMA 7, SEX

Node 2: Stanford Research Institute (SRI) (1 October) - SDS940/Genie

Node 3: University of California Santa Barbara (UCSB) (1 November) - IBM 360/75, OS/MVT

Node 4: University of Utah (December) - DEC PDP-10, Tenex

https://www.zakon.org/robert/internet/timeline/

And a network sketch:

https://www.scientificamerican.com/gallery/early-sketch-of-a...