Typically Walmart is located on the outskirts of a major town/city. The advantage is the availability of a large parcel of real estate at a very cheap rate. Plus, it gives easy access to major highways which are critical for timely movement of goods from warehouses to retail stores - which means trucks will spend lesser time navigating inner city traffic / roads and the time to ship goods between source to destination is lesser all over - leading to savings in time, labour & fuel!