Yvon Chouinard mentions this in his excellent book “Let My People Go Surfing,” where he says the furthest you can get from a road in the lower 48 is about 20 mi

Yvon Chouinard mentions this in his excellent book “Let My People Go Surfing,” where he says the furthest you can get from a road in the lower 48 is about 20 miles, near the headwaters of the Snake River in Wyoming. Cool to see some methodology that lines up with that estimate.