The Jerusha Dewey Cottage is on the grounds of Clayton, in Roslyn NY. I visited it on October 8, 2008. The cottage is not open to tour. It was the guest house for William Cullen Bryant and it was built in 1862.
There are many paths to walk in the woods at Clayton. The Jerusha Dewey Cottage is located off one of them. Here is a view of the path near the cottage.