The 52c stamp on the upper-right corner was issued in 2007 celebrating 150 years of Ottawa as Canada's capital.
On December 31, 1857, Queen Victoria was asked to choose a common capital for the Province of Canada (modern day Ontario and Quebec) and chose Ottawa. While Ottawa is now a major metropolis and Canada's fourth largest city, at the time it was a sometimes unruly logging town in the hinterland, far away from the colony's main cities, Quebec City and Montreal in Canada East, and Kingston and Toronto in Canada West.
The Queen's advisers suggested she pick Ottawa for many important reasons: first, it was the only settlement of any significant size located right on the border of Canada East and Canada West (today Quebec and Ontario), making it a compromise between the two colonies and their French and English populations; second, the War of 1812 had shown how vulnerable major Canadian cities were to American attack, since they were all located very close to the border, while Ottawa was then surrounded by dense forest far from the border; third, the government owned a large parcel of land on a spectacular spot overlooking the Ottawa River. Ottawa's position in the back country made it more defensible, while still allowing easy transportation over the Ottawa River to Canada East, and the Rideau Canal to Canada West. Two other considerations were that Ottawa was at a point nearly exactly midway between Toronto and Quebec City (~500 km/310 mi) and that the small size of the town made it less likely that politically motivated mobs could go on a rampage and destroy government buildings, as happened in the previous Canadian capitals. The Ottawa River and the Rideau Canal network meant that Ottawa could be supplied by water from Kingston and Montreal without going along the potentially treacherous US-Canada border.
In 1866, the legislature was finally moved to Ottawa, after a few years of alternating between Toronto and Quebec City.