In which decade did the first self-service grocery store layout (where customers select their own products) replace the traditional clerk-service model in American retail?

Before the convenience of online shopping and self-checkout lanes, retail stores underwent a fascinating evolution. The layout and design of stores have transformed dramatically over the decades, influencing consumer behavior and shopping patterns. This trivia question explores a pivotal innovation in store layouts that forever changed how we shop. Test your knowledge of retail history and see if you can identify when this revolutionary change occurred!

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1910s (Piggly Wiggly's innovation)
1930s (Post-Depression retail reform)
1950s (Post-WWII consumer boom)
1880s (Department store revolution)