Norway maple (Acer platanoides).
From Wikipedia:
“Norway Maple has been widely placed into cultivation in other areas, including western Europe northwest of its native range. It grows north of the Arctic Circle at Tromsø, Norway. In North America, it is planted as a street and shade tree as far north as Anchorage, Alaska, having been first introduced from Europe in the 18th century.
During the 1950s-60s, it became popular as a street tree due to the large-scale loss of American Elms from Dutch Elm Disease.
It is favored due to its tall trunk and tolerance of poor, compacted soils and urban pollution, conditions that Sugar Maple cannot grow in. Because of the Norway Maple’s invasive nature, the London plane, Platanus X acerifolia, is often recommended as a pollution tolerant urban tree for planting where trees cannot be allowed to freely colonise new areas.”
Westmount Overlooked 