In 1916, the first self service supermarket, the "Piggly Wiggly" was opened by Clarence Saunders in Memphis, Tennessee. Prior to it's opening, grocery stores didn't allow customers to gather their own goods. Instead, they would give a list of what they wanted to a clerk who would collect them.
Piggly Wiggly introduced the innovation of allowing customers to go through the store, gathering their goods, which lowered costs and allowed Saunders to offer lower prices. Customers at Piggly Wiggly entered the store through a turnstile and walked through four aisles to view the 605 items sold in packages and organized into departments. The customers selected merchandise as they continued through the maze to the cashier.
Other stores started to experiment with similar formats, which for a short time became known as "groceteria", after cafeterias which were another new concept at the time.
Beyond the initial innovative idea, Piggly Wiggly led the way with other innovations that we take for granted today. Their new style of shopping led to products improving their packaging so that their brands were instantly recognizable. They were also the first to provide check out stands, mark prices on every item in the store, and in 1937, they were the first to provide customers with shopping carts.
At its peak, the company operated 2,660 stores and posted annual sales in excess of $180 million. Saunders attempted a squeeze based on the substantial short interest in the stock, which drove the price up from $40 to $120 and creating millions of profit on paper. Following this, the company was divided into strategic units and sold to regional grocery chains, including Kroger & Safeway.