Arthur filmed at de Seversky Mansion, Old Westbury. Arthur travels here to propose to Susan at her family's estate, which is now owned by an institute. On screen it's Susan Johnson's family estate.
Probable Named in published production coverage; the coordinate is the place itself, checked against a gazetteer.
Planning the trip? The United States travel atlas covers money, language and getting aroundand everything filmed in Old Westbury is on one page
Venture keeps every scene location on one map, sorted by how far you'd have to walk. Open it in Old Westbury and it tells you what was shot around you, how to get there, and whether you can actually go in.
Download Venture for iOS Android