The development of the covered hopper car for the transport of bulk commodities for the agricultural, chemical, and construction industries entered a new phase in the late 1940s, when the shops of the Canadian Pacific Railroad introduced a 70-ton, 3000 cubic foot, interior braced hopper with smooth, welded sides similar in appearance to the Canadian offset side open hoppers of the era. This "slab side" design actually maximized the interior width of the car, thereby lowering the center of gravity and improving tracking stability. Cars of this design were produced from 1950-1964 by National Steel Car Company, Canadian Car and Foundry, Marine Industries, and even Montreal Locomotive Works. Over the years of production, a number of different roof hatch arrangements for product loading were available, and the openings along the side sills - an early design change made by CP to give better access to the discharge mechanisms - became standard on all cars produced after 1954. These cars were a common sight on Canadian and US rails through the late 1990s hauling grain, malt, sugar, cement, or even in company sand service. The Atlas model of this distinctive car is available in 6, 8, and 12 hatch versions, with or without the side sill openings.