The final decades of the nineteenth century are often called "the Gilded Age," a satirical term taken from the title of one of Mark Twain's lesser-known novels. This was a time of rapid industrial and economic expansion, when leading industrialists were able to make vast fortunes. The following men were some of the leading captains of industry, or wealthiest "robber barons" of the era, depending on your perspective. Adjusted for inflation, their fortunes are some of the greatest ever accumulated. Andrew Carnegie, for instance, made over $350 billion in today's terms, while John D. Rockefeller's fortune was even larger at around $400 billion. Henry Clay Frick's mansion on the Upper East Side of Manhattan is now an art museum, filled with the priceless works he collected. The Morgan Library, also in Manhattan, has a collection which includes three Gutenberg Bibles, estimated to be worth well over $100 million.

Andrew Carnegie was born in Scotland and came to America at the age of 12. He was a leader in the expansion of the steel industry and founded the Carnegie Steel Company in Pittsburgh.

Henry Clay Frick was Chairman of the Carnegie Steel Company and was himself the founder a coke manufacturing company, as well as having extensive interests in railroad construction and real estate.

Meyer Guggenheim was born in Switzerland and came to the United States at the age of 19. He made his fortune in silver mining and ore smelting.

John Pierpont Morgan is primarily known as a banker, but he also had extensive industrial and agricultural interests. He was involved in founding some of the largest industrial corporations of the period, such as US Steel.

John D. Rockefeller is widely regarded as the richest American of all time, and the richest person in modern history. His wealth came from the Standard Oil Company, which he founded in 1870 and ran until 1897.

Cornelius Vanderbilt made his money in transportation, principally railroads and shipping. He was the owner of the New York Central Railroad.