The old National Gypsum Company started its mining operations in Nova Scotia on the northern island of Cape Breton when it purchased Atlantic Gypsum in 1936. There were two operations on the island – Cheticamp which produced 182,000 tons in 1937 and Dingwall which produced 75,000 tons.
Chitcamp closed at the start of World War II and never reopened.
Dingwall was in full production after the war, but harsh winters and a shallow port limited production to the months of May through November. Each spring the channel had to be dredged and, toward the end of the shipping season, cargo size was reduced to keep the vessels afloat. Because of its northerly location, daylight in the summer lingered until 10 p.m., allowing Dingwall to easily work the quarry on a two-shift basis.
At that time, the company owned three ships – Cheticamp, Dingwall, and Walton. With luck, a vessel leaving Dingwall could be at the company's Savannah Plant in five days.
The Dingwall operations closed in 1955 when Milford Station, 30 miles from Halifax, went into full production.
The company removed tailings and restored the land at the Dingwall site.