Much of the movie was filmed at the Mohonk Mountain House near New Paltz, New York, a Quaker-family-owned hotel, built in stages from 1879 to 1910. It's situated on the Shawangunk Ridge, which is south of the Catskill Mountains.
On her nude scene, Camryn Manheim said, "It was a mortifying experience to get naked in front of a room full of 50 people, when I hadn't been naked in a room full of one person in a hell of a long time. The only way I was able to do it was by saying to myself, 'If we're ever going to dispel the myth that fat women aren't beautiful, then some woman is going to have to get naked and be beautiful.'"
In the film, Kellogg is depicted as being in good health until his apparent death of a heart attack while speaking to reporters. In reality, his sight, hearing, and sense of taste, were rapidly deteriorating toward the end of his life, and in late fall of the year he died, he had developed Bell's palsy, which caused the left side of his face to droop. On December 11, he developed an acute case of bronchitis and pneumonia accompanied by severe coughing and shortness of breath. Two days later, in the evening, he slipped into a coma, from which he never awoke. He died the next day, December 14, 1943, half an hour before midnight.
When the Lightbodys arrive at the sanitarium the trees are bare, without leaves. The next day Eleanor is riding a bicycle in the woods and the trees are all covered with leaves.