Andrew Carnegie in Pittsburgh

As a businessman, Andrew Carnegie was ruthless toward competitors and workers, but upon his retirement he gave most of his wealth away, becoming in the process one of America's greatest philanthropists. Much of his enormous gift-giving was bestowed upon Pittsburgh and its environs.

His charitable works were not just a guilty afterthought to a life of ruthless acquisition. Carnegie wrote in a famous article known as the "Gospel of Wealth" that a talented businessman is entitled to great wealth, but he has a duty to live without ostentation, provide modestly for his dependents, and help his "poorer brethren, bringing to their service his superior wisdom, experience, and ability to administer."

Carnegie's tone is patronizing in titan-of-industry style, but his works have the better of the argument. The wisest fields for philanthropy, he wrote in 1889 are universities, libraries, hospitals, parks, concert halls, swimming pools, and church buildings.

Critics may carp that homes should come before swimming pools, and that the "libraries" were just buildings without books, but many of the 2, 509 Carnegie libraries endure, as do Carnegie Mellon University in Pittsburgh, the Carnegie Endowment for International Peace, and the Carnegie Institution of Washington, D.C., New York City's Carnegie Hall, and many other structures and entities financed by his $350 million in gifts.