18.76 miles. You can drive this distance in 15 minutes on a freeway. But it is also the furthest away you can get in the “Lower 48” US states from roads, machines, and motors.
How much uninhabited space do you need before it counts as “wilderness“, and what counts as “uninhabited“? Does the backyard of a 0.1-acre property have several square feet of wilderness? Is an undeveloped 0.25-acre plot a quarter-acre of wilderness? If highway traffic can be heard constantly throughout a 1000-acre wetland, or if a 1000-acre woodland has a walking trail, then is that area wilderness? If a particular area of 1000 square kilometers is logged or fished only once a decade, is it wilderness? Is even 100,000 square miles still wilderness if it is filled with radio waves, its skies are routinely flown over, its waters are downstream from the effluent of civilization, its animals are harvested should they ever wander or migrate outside its borders, or microscopic synthetics (e.g. plastics) can be found in every specimen of its ecosystem?