I know these aren't necessarily the middle of nowhere, but it's the best I know of for my area.
Model 5/7 in Flintstone, MD from I-68:
Sentry 3V8H or 7V8 in Burnsville, WV from I-79:
ACA Screamer in Reynolds Store, VA from US-522 (not an interstate but a major thoroughfare for the area):
Historic preservation student in Eastern WV.
As a child, I lived near a Sentry 10V fire siren that scared the jeebers out of me. Now I love sirens and that very same 10V is my profile picture!
My West Virginia siren map