During the early 1970s, Crowther worked at defense contractor and internet-pioneer Bolt Beranek and Newman (BBN), where he was part of the original small ARPAnet development team.

His implementation of a distributed distance vector routing system for the ARPAnet was an important early step in the evolution of the Internet.

[1] Following his divorce from his wife, Crowther used his spare time to develop a text-based adventure game in Fortran on BBN's PDP-10.

Crowther agreed, and Woods developed several enhanced versions on a PDP-10 housed in the Stanford Artificial Intelligence Laboratory (SAIL) where he worked.

Crowther and his first wife Pat were active and dedicated cavers in the 1960s and early 1970s—both were part of many expeditions to connect the Mammoth and Flint Ridge cave systems.

[8] As a member of the MIT Outing Club during the late 1950s and early 1960s, Crowther also played an important role in the development of rock climbing in the Shawangunks in New York State.

[citation needed] Some of these routes sparked controversy because protection bolts were placed on rappel, a new tactic that Crowther and several others began to use at the time.