Final answer:
Charlie Chaplin was the most popular slapstick comedian in the United States during the 1920s, captivating audiences with his tramp character.
Step-by-step explanation:
The most popular slapstick comedian in the United States during the 1920s was Charlie Chaplin. This sad-eyed tramp with a moustache, baggy pants, and a cane was the top box office attraction of his time. His recurring character, known as 'The Tramp', appeared in many of his silent films and resonated with audiences across the nation.