http://www.datapointed.net/2010/09/distance-to-nearest-mcdon...
There are massive swaths of land in the lower 48 that are pretty much untouched beyond a few footpaths that are rarely used.
https://www.bbc.com/news/world-us-canada-42104894
The best one can do is 21 miles from a road - in Yellowstone
Sugar bunker, just NW of Las Vegas has a few places with 50km (~30 miles) though.
https://www.google.com/maps/@39.7775746,-122.9327754,2401a,3...
A forestry or old logging road that hasn’t been used in 50 years doesn’t come to mind.
Virtually no forest service roads are older than 50 years old, as most were constructed after WW2 to assist in logging.
You’re splitting hairs.
The entire country has been surveyed, so of course it's been touched (as defined by some human presence at some point in time).