During the Gilded Age, the prominent figure known as a "railroad tycoon" is Cornelius Vanderbilt. He was a major player in the expansion of the railroad industry in the United States and played a significant role in shaping the transportation sector during that era.
John D. Rockefeller was known for his impact on the oil industry, Andrew Carnegie was a steel magnate, and Upton Sinclair was a writer and social activist, known for his works criticizing labor conditions, most notably in "The Jungle."