Canada Centenary Issue
On May 25, 1967, the Canada Centennial stamp was issued in Montreal – the first time a US stamp had a First Day ceremony in another country.
The stamp, designed by Ivan Chermayeff, was first made available at the United States Pavilion at Expo ’67 in Montreal Canada. The First Day Covers created there were the first US covers with a first-day cancellation from another country. The stamps were then made available at US post offices the following day.