Charles Sumner Frost was an American architect. He is best known as the architect of Navy Pier and for designing over 100 buildings for the Chicago and North Western Railway.

Navy Pier is a 3,300-foot-long (1,010 m) pier on the shoreline of Lake Michigan, located in the Streeterville neighborhood of the Near North Side community area in Chicago, Illinois, United States. Navy Pier encompasses over 50 acres (20 ha) of shops, restaurants, live theaters, family attractions, parks, gardens, and exhibition facilities and is one of the top destinations in the Midwestern United States, drawing over nine million visitors annually. It is one of the most visited attractions in the entire Midwest and is Chicago's second-most visited tourist attraction.