Rachel Askinasi/Business Insider Walmart is the largest brick-and-mortar retailer in the world in terms of sales. Walmart has only three different store formats across the US: Walmart Discount Store Stores, Walmart Supercenters, and Walmart Neighborhood Markets. While the Discount Store store model is the original — founder Sam Walton opened the first one in 1962 — there are now two times more Supercenters — which were first developed in 1988 — than there are Discount Store stores, according to Walmart.