Conversation so far:
How come Cornelius Vanderbilt focused on steamboats?
A ferry entrepreneur named Thomas Gibbons asked Vanderbilt to captain his steamboat between New Jersey and New York. Although Vanderbilt kept his own businesses running, he became Gibbons's business manager.

Question: How did he make all his money?
Self-contained rewrite: How did Cornelius Vanderbilt make all his money?