Having studied in a university named after these two sons of Pittsburgh, I just have to link to Matthew Price's review of Andrew Carnegie and Andrew Mellon: An American Life:
... [T]hese Pittsburgh powerhouses helped define and shape an epoch of American capitalism when this country actually made things (who’s the Chinese Carnegie?), when Steel Town was true to its name—a belching, soot-covered mess otherwise known as “hell with the lid off.” Carnegie, a bumptious little Scotsman who swaggered as if he were twice his size, soared with iron and steel, smashing unions along the way—Carnegie’s tactic was to conciliate, then crush—as he piled up a vast fortune; when he sold Carnegie Steel to J.P. Morgan in 1901, he walked away with $120 billion (in 2006 dollars), which he used to underwrite a hodgepodge of philanthropic causes, foundations and charitable trusts. (Next time you walk by a branch of the New York Public Library, thank Mr. Carnegie). A self-taught, self-righteous know-it-all, he lectured the world—like George Soros, he wouldn’t ever shut up—in his voluminous writings on many topics, counseled the rich to give away their money, and embarked on a quixotic campaign to bring about world peace, even if part of the Carnegie fortune came from the U.S. Navy, which bought armor plates manufactured in Carnegie mills.
The life of Andrew Mellon offers a prim study in contrast with his fellow western Pennsylvania capitalist. Whereas Carnegie was a sunny extrovert, Mellon was a shy, pallid, unfunny, emotionally stunted man who loathed the spotlight. He was no activist, nor was he, as Mr. Nasaw writes of Carnegie, a “moral philosopher of industrial capitalism.”
An entrepreneur of genius, Mellon let his endeavors speak for themselves. Mellon money helped kick-start everything from Alcoa to Gulf Oil, and flowed through almost every sector of the American economy, from banking to gas, metals and mining. A discerning, indefatigable art collector, he was the driving force in the creation of the National Gallery. In his three terms as a tax-cutting Secretary of the Treasury, he saw the 20’s roar (even if he didn’t), then crash. ...