The Palmer House, Chicago
Now a Hilton, and called by at least one source the “longest continually operating hotel in North America,” the online reviews are great fun to read. Without doubt the property has been there, staid and solid, as long as anyone can remember. Two unattributed cards are available, one unused (Grade: 1, $1) and one mailed in May 1941 with stamp and postmark and wildly inappropriate message (Grade: 2, $2).