Hyak was established around 1915 at the eastern portal of the Snoqualmie Pass Milwaukee Road Railroad tunnel.
https://github.com/davepinch/pinchy.cc/blob/master/content/topics/places/cities/united-states/washington/kittitas-county/hyak/hyak-washington.md
Hyak, Washington (Wikipedia) Hyak is an unincorporated community located on Snoqualmie Pass in Kittitas County, Washington. It is located within the Snoqualmie Pass CDP.