Final answer:
Mark Twain was the anti-imperialist writer and satirist in the late 19th century.
Step-by-step explanation:
The anti-imperialist writer and satirist in the late 19th century was Mark Twain. Mark Twain, whose real name was Samuel Longhorn Clemens, is known for his travel writings, storytelling, and novels and short stories. His most famous novel, Adventures of Huckleberry Finn, is often considered the 'Great American Novel.'