Final answer:
Robert Fulton, an American inventor, built the first successful steamship in the United States in 1807.
Step-by-step explanation:
Robert Fulton, an American inventor, is known for building the first successful steamship in the United States in 1807. The steamship, called the Clermont, used a steam engine to propel itself along the Hudson River. Fulton's invention revolutionized water transportation by replacing the dependence on wind power with steam power. Therefore, the correct answer to the question is d) Robert Fulton.