Given that Detroit is a large city and the destination point being just Mount Rushmore with no specific location within the area, distances will differ. The shortest route by car is approximately 1,217 miles and will approximately take 20 hours and 20 minutes to drive to from Detroit (toll booths and restricted roads aren't taken into consideration - further restrictions from blocked-off roads will affect this too) if you drive down the I-90W route. Other suggested routes will have you using the I-80W and I-94W roads which add only 30 miles to the distance and 12 minutes to the time but may be needed to be used if roads close off elsewhere.
By walking, the distances will also differ because weather and road restrictions will hinder your chances of arriving at Mount Rushmore should such events occur. Again, as an estimate, the smallest available walking distance is 1,129 miles should you pass through Muskegon and the S Dakota W route as part of your path ,yet certain minor pathways and sidewalks aren't taken into consideration so distances will vary, and the approximate walking time for this route is 14 days and 10 hours (this time is calculated if you walked to Mount Rushmore 'all in one go', as though you traveled without resting, eating or sleeping).
The actual distance from Detroit (MI) to Keystone (SD) is 1029.84 miles and Mount Rushmore is approximately 3 miles from Keystone itself so the actual distance from Detroit to Mount Rushmore is between 1032 - 1033 miles, yet the extra 200 or so miles is added to the distances by walking and car namely because of the detour needed to get around Lake Michigan (it's not advised to travel straight through it unless there is a ferry service nearby). The actual distance will differ depending on whether your destination is at the foot or top of Mount Rushmore or whether your set-out point is on the edge of Detroit or not.
By walking, the distances will also differ because weather and road restrictions will hinder your chances of arriving at Mount Rushmore should such events occur. Again, as an estimate, the smallest available walking distance is 1,129 miles should you pass through Muskegon and the S Dakota W route as part of your path ,yet certain minor pathways and sidewalks aren't taken into consideration so distances will vary, and the approximate walking time for this route is 14 days and 10 hours (this time is calculated if you walked to Mount Rushmore 'all in one go', as though you traveled without resting, eating or sleeping).
The actual distance from Detroit (MI) to Keystone (SD) is 1029.84 miles and Mount Rushmore is approximately 3 miles from Keystone itself so the actual distance from Detroit to Mount Rushmore is between 1032 - 1033 miles, yet the extra 200 or so miles is added to the distances by walking and car namely because of the detour needed to get around Lake Michigan (it's not advised to travel straight through it unless there is a ferry service nearby). The actual distance will differ depending on whether your destination is at the foot or top of Mount Rushmore or whether your set-out point is on the edge of Detroit or not.