On June 9, 1978, Canada opened its second international stamp exhibition, CAPEX ’78 (CAnadian Philatelic EXhibition). The first time had been in 1951.
The exhibition was held to mark the 100th anniversary of Canada joining the Universal Postal Union (UPU). The UPU was established in 1874 to make sending international mail easier. Canada joined the organization on July 1, 1878.