In in northern central Massachusetts, near the Connecticut river, in a town called Greenfield.
There are stone structures in New England- some controversy exists about the exact origin of many of them as so many sites were pulled apart for the stones by western settlers. I and a friend once discovered a stone storage cellar years after we'd known it as a small hilly bump in the ground. The slab of rock that had been the roof had broken and caved in.
There is a site about a two hour drive from here called 'Mystery Hill" in New Hampshire that I mean to check out soon. It's also suffered from having been gleaned for stones but much of it remains, and it most certainly is an astronomically oriented site. Nobody is really sure who built it, tho it is doubtful that it's the work of modern people.There is evidence that the Vikings came and went along the northeastern seaboard of the US. Some evidence suggests a Nordic origin (!)- However, it seems more likely that it was the work of some native people from the past.