Which man controlled much of the railroad industry by the late 19th century?

Cornelius Vanderbilt

Explanation:

Cornelius Vanderbilt was a millionaire that ruled the railroad industry in the 19th Century. He started with steamboats, later he made a profit with the ferry between New York City and New Jersey. Later he created his fleet of boats and expanded the ferry to other cities in Long Island.

When the California Gold Rush came, he started to transport people from the West Coast to Central America, when he noticed the railroad system was very profitable he began buying stocks. By 1860s he bought several railroads in New York and united them creating the New York Central and Hudson River Railroad.

The answer is Cornelius Vanderbilt