Arkansas-based WalMart operated Hypermart USA, their original (200,000+ square foot) brand of grocery and dry goods superstore, between 1987 and 1990. The prototype Hypermart USA was simply too large to maintain and navigate. The smaller SuperCenter, introduced in 1988, became the company's standard superstore model.
Graphic from www.walmart.com

The SuperCenter averages 185,000 square feet, but smaller stores, in the 120,000 square foot range, are being built. This location, part of Bucks County, Pennsylvania's LEVITTOWN TOWN CENTER, opened in July 2009. It was among a group of stores that replaced the historic LEVITTOWN SHOP-A-RAMA, a circa-1953 open-air mall. 
Photo from www.storetrax.com

Our first present-day Shopping Mall Supermarket site plan depicts Phoenix, Arizona's CHRISTOWN SPECTRUM and its SuperCenter-Costco-SuperTarget layout. The original mall, what little that is now left of it, dates to 1961. Its WalMart originated in the 1990s as a conventional "Region One" store, but was expanded into a SuperCenter in 2003. Target's CHRISTOWN location is the mall's newest addition. It welcomed first patrons in October 2007.