I live close to Henry Fords estate, wide open to walk around but of course MD not legally possible - I am guessing they would lol if you asked permission to detect, then escort you off the premises.
He was well known to have large social gatherings there, there are some old dilapidated ponds on the grounds [just out of the picture], I have seen pics from back in the day with 100's of socialites gathered around the ponds [which were swimming pools then], granite steps, arches, band stage, the works.
This place is now truly reclaimed by nature, in fact that is exactly what most of the grounds are now outside of the estate itself, a nature preserve. Can still see and walk on the granite steps, some arches are still standing, and portions of the stage still remain last time I was there [been a few years]
Here is Ford with Thomas Edison, Warren G. Harding, and Harvey Firestone somewhere on the grounds - Cabin actually still exists but has been moved extensively over the years due to a nearby college campus.
The field where he was born and raised[about 3 miles from here, not pictured]
is still largely a field believe it or not, that I have detected but have found nothing so far. Ground very hard and clumpy and things are still grown there, so it is either filled with stumps and roots or has stuff growing and can turn into a mud pit quick, tough area to detect. A good % has been developed, probably a matter of time before it all is.
1st shot shows general estate area, quite extensive. Large Ford Made waterfall on the grounds, remains of a couple old boat houses still intact in the vicinity.
2nd pic shows cabin I was talking about, almost certainly the same one pictured above, and almost certainly not the original location
3rd pic shows the pond area where he had alot of social gatherings back in the day, now the home of mosquitoes, groundhogs and frogs. Some of them obviously have been filled in and only the large one remains, too bad. Maybe a safety measure as they filled with stagnant water and people go walking back there unregulated all the time in the summer.
4th pic shows more ruins on the estate - Not sure what this area was for, confidant it had something to do with entertaining large crowds of associates
edit: Pic of the 4 men above is apparently NOT Fords estate but rather from a camping trip in Maryland in 1921.
Area & Inn History - Lake Pointe Inn
There is a pic of him and famous personalities on his estate grounds with the cabin in the background, I'll see if I can dig it up