Strangle enough I've been thinking along the same lines over the last summer.
Check out the NYSDB.org website, it's he local Blacksmithing group.
Typically iron foundries where site "close" to iron sources in the early 1800's. Constantia, NY had Iron Foundries, seems to have dried up and gone away in the middle 1800's, Apparently there is a "Decent" amount of Bog Iron in Lower Oswego County Swamps.
So the bog iron sources have had 150 years to rebuild.
The geological surveys I've read on the early 1800's are vague about exact sites in Oswego County, Way back when, traveling about the mosquito infested swamps, must have been too much work.
I'm told that the waterways are free, so as long as you stay in the stream, you're safe?
I plan to go looking for Bog Iron next summer.
Take Care.