Morgan reorganized and consolidated several financially unstable railways in the late 19th century, when the U.S. railroad business was overexpanded and competitive (the first transcontinental rail line was constructed in 1869). He acquired large sections of these railroads' stock and controlled an estimated one-sixth of America's rail networks. After hitting an iceberg, White Star's Titanic sank on its maiden trip. Morgan, who attended the ship's 1911 christening, cancelled the April 1912 sail.

Morgan used his influence to save the US during multiple economic crises when there was no central bank. Morgan led a banking syndicate that funded the federal government $60 million in 1895 to save the gold standard. In 1907, Morgan convened a gathering of the nation's leading bankers at his New York City residence to encourage them to bail out failing financial companies to stabilize markets.

Morgan was initially praised for leading Wall Street out of the 1907 financial crisis, but muckraking journalists, progressive politicians, and others began to accuse the portly banker with the handlebar mustache and gruff manner of having too much power and manipulating the financial system for his own benefit. In 1912, Morgan testified before a congressional committee sponsored by Louisiana Representative Armand Pujo (1861-1939) examining the "money trust," a small group of elite Wall Street financiers, including Morgan, who allegedly cooperated to control American banking and industry. The Pujo Committee hearings helped establish the Federal Reserve System in December 1913 and approve the Clayton Antitrust Act in 1914.

Morgan gave millions to nonprofits. He donated art to the Metropolitan Museum, American Museum of Natural History, American Academy in Rome, Wadsworth Atheneum, and Yale University.