Denny's was founded by Harold Butler and Richard Jezak in 1953. Their restaurant was named Danny's Donuts. By 1956, Jezak sold his stake in the restaurant and Butler changed the concept from a donut shop to a coffee shop. The now eight restaurant chain was renamed Danny's Coffee Shops and were open 24 hours. In 1959, the name was changed to Denny's Coffee Shops in order to avoid confusion with another restaurant chain named Coffee Dan's. In 1961, the name was shortened to Denny's. In 1977, Denny's introduced the Grand Slam breakfast. By 1981, Denny's had over 1,000 restaurants in all 50 states.