A Usenet map dated April 5, 1981. Most of the sites are in the Research Triangle area of North Carolina, Bell Labs, Berkeley and some other Bay Area sites, and UCSD. Reed College is an outlier. Very important: decvax, from the Digital Equipment Corporation, later to become a major long haul hub.
https://files.mastodon.lawprofs.org/media_attachments/files/112/299/535/080/565/914/original/293e7b34f2ca7975.jpeg