Where was A Letter to Three Wives filmed?

1949 film by Joseph L. Mankiewicz

A Letter to Three Wives (1949) was filmed in Los Angeles, Hudson River, Stamford, Cold Spring, Mahopac and Hook Mountain State Park, 6 places named in its Wikipedia article, in the United States. Wikidata records no filming location for it at all, so the article is the only recorded source. Each place says where its claim comes from.

See them on the map → Wikipedia Source data