Pro-Cathedral of the Assumption, Limestone pro-cathedral in North Bay, Canada.

The Pro-Cathedral of the Assumption is a Roman basilica-form church in North Bay, rectangular and oriented south to north, with a grand entrance, long nave and apse. It rests on long iron rod piles driven through quicksand and thin hardpan; the foundation is North Bay granite, while the superstructure is white limestone from a quarry in Orillia, Ontario.

Construction began in 1904 when Father David Joseph Scollard initiated the expansion to accommodate the growing population of the town. The development was driven by railway expansion that brought workers and settlers to the region.

The name reflects its role: a pro-cathedral stands in place of a cathedral, since the bishop of Sault Ste. Marie chose to reside in North Bay rather than at the diocesan seat. The parish began as St. Mary's of the Lake, whose bell once served as the town's fire alarm and whose sacristy upper floor doubled as a schoolroom.

The church stands on iron rod piles driven through quicksand and thin hardpan, with a foundation of North Bay granite. It runs south to north along the site: grand entrance, long nave, apse. The single steeple rises about 146 feet, raised another 20 feet when the cross was reset by helicopter in the 1980s.

The building features a single tower instead of the two towers typically found on traditional cathedral structures. This distinctive design makes it instantly recognizable and gives it a unique presence in the town's skyline.