Port Arthur was a city in Northern Ontario, Canada, located on Lake Superior. In January 1970, it amalgamated with Fort William and the townships of Neebing and McIntyre to form the city of Thunder Bay.

Fort William was a city in Ontario, Canada, located on the Kaministiquia River, at its entrance to Lake Superior. It amalgamated with Port Arthur and the townships of Neebing and McIntyre to form the city of Thunder Bay in January 1970. Since then, it has been the largest city in Northwestern Ontario. The city's Latin motto was A posse ad esse, featured on its coat of arms designed in 1900 by town officials, "On one side of the shield stands an Indian dressed in the paint and feathers of the early days; on the other side is a French voyageur; the cent[re] contains a grain elevator, a steamship and a locomotive, while the beaver surmounts the whole."