Here in Washington, as almost everywhere else in America, his mark is inescapable. The Carnegie Library at Mount Vernon Place, a model of the Beaux Arts style, was donated to the city by him in 1902, along with three branch libraries. The neoclassical building of the Carnegie Institution, on P Street, is one of the city's architectural glories and the headquarters of one of the world's most important centers of scientific research. On Massachusetts Ave., the Carnegie Endowment for International Peace continues its valiant, hopeless struggle against humankind's baser inclinations, and on New York Avenue the Washington office of Carnegie Mellon University conducts many activities of local, national and international importance.

Carnegie's story is right out of Horatio Alger, though he makes Ragged Dick look like a mere piker. The poor Scot arrives in Pittsburgh in 1848, age 12, child of an aimless father and industrious mother. Goes to work at an early age and quickly ingratiates himself to all with "his remarkably sunny disposition, his broad smile, and non-stop, good natured chatter" -- not to mention his capacity for hard work and his nimble mind. Soon he is a messenger boy for the telegraph office -- "the perfect position for an ambitious, affable young man" -- and soon after that becomes a telegraph operator, "the most sought-after operator in the company" because he is the smartest and the quickest. On he moves to the Pennsylvania Railroad, not yet 20 years old, and wins the favor of its president-to-be. He's offered the opportunity to buy shares in another company, and eagerly does so, with a loan from the boss, and later gets his first dividend check.

"I shall remember that check as long as I live," he wrote many years later. "It gave me the first penny of revenue from capital -- something I had not worked for with the sweat of my brow. 'Eureka!' I cried. 'Here's the goose that lays the golden eggs.' " With that he was off. During the Civil War he helped keep the trains running -- he paid $850 to an Irish immigrant to take his place in the army -- and began to make farsighted but prudent investments. "Meteoric" scarcely begins to describe his upward trajectory:

"Almost thirty, Andrew Carnegie was the principal shareholder in several thriving companies, a partner in several more, and a force in local business circles, well known and respected for his acumen and his access to capital. He paid taxes on an income of $17,500 in 1864, with an additional $1 tax for his one-horse carriage. A year later, his income had risen to $38,735 ($5.6 million today), on which he paid a tax of $3,655. Again, he was charged an additional $1 tax for his carriage, $2 for his gold watch, and $4 for his pianoforte."

It is an astonishing story and even now, almost nine decades after his death, one that is familiar to many Americans. Carnegie, after all, is the giant of the Gilded Age, his only real rival being his contemporary and friendly acquaintance John D. Rockefeller. Never has this story been told so thoroughly or so well as David Nasaw tells it in this massive and monumental biography. Nasaw, who teaches history at the City University of New York and is the author of an excellent biography of William Randolph Hearst, has gotten access to a great deal of material unavailable to previous biographers and has made the most -- at times too much -- of it. Andrew Carnegie would be a better book had it been pared down from 800 pages of text to, say, 650, because Nasaw is in love with his research and cannot let go of it even when it becomes redundant, but only readers laboring under constraints of time are likely to complain; this is biography on the grand scale, and on the whole it lives up to its author's ambitions.

Not the least of its qualities is that Nasaw, unlike most biographers of prominent public figures, does not scant the private side of his subject's life. He trowels on all the details about how Carnegie became richer and richer and richer -- he was both the beneficiary and the victim of what Nasaw wryly calls "the inexorable logic of compound interest" -- and how in March 1901 he sold out to J.P. Morgan for the then-unimaginable sum of $400 million, making possible the formation of U.S. Steel, but he is no less attentive to Carnegie's intimate and inner sides. He admires his subject -- "one of the most fascinating men I have encountered, a man who was many things in his long life, but never boring" -- but sees him with eyes wide open, and thus paints a portrait that is balanced, nuanced and, in the end, fair and probably accurate.

Nasaw doesn't dwell overlong on Carnegie's physical stature, but probably that is where one must start. Samuel Clemens, who was one of his many famous friends, wrote that "Mr. Carnegie is no smaller than Napoleon, . . . but for some reason or other he looks smaller than he really is. He looks incredibly small, almost unthinkably small." To the end of his life Carnegie was "the undersized outsider with the funny accent who had been uprooted from his home" in Scotland and never forgot it. His "insecurities were legion," but he "battled his demons and insecurities in silence. He was a master at compartmentalizing his life, building barriers between Carnegie the lovesick suitor, Carnegie the powerful industrialist, and Carnegie the man of letters, disciple of Herbert Spencer, and confidant of Matthew Arnold."

Apart from his mother and wife, Herbert Spencer almost certainly was the most important influence in Carnegie's life. The British philosopher is now almost entirely forgotten outside academic circles, but in the second half of the 19th century he was one of the most influential and widely read writers in the West. He and Carnegie became friends of sorts -- Spencer seems to have been singularly disagreeable and antisocial -- but that meant less than the philosophical underpinnings Spencer provided for Carnegie. He was a gloomy man but a sunny moralizer: "Spencer offered Carnegie and his generation an intellectual foundation for their optimism, their sense that history was a record of forward progress, by arguing that material progress went hand-in-hand with moral progress, that industrialization was a higher state of civilization than that which preceded it, and that the future would be even rosier than the present."

Spencer taught Carnegie that "his success as a businessman . . . depended on his adherence to the laws of the marketplace, which, because they were embedded in a larger evolutionary schema, were as moral as they were inexorable. The path of evolutionary progress he was following would be strewn with hardships and sacrifice; but these were unavoidable in the short term if mankind was going to benefit over the long term." Hardships and sacrifice were far more likely to be exacted upon the laboring classes than upon their wealthy employer; this was regrettable but also unavoidable, because it was toward the greater goal of putting sufficient money into the hands of Carnegie and his peers so that they could redistribute it for the benefit of all.

Carnegie devoutly believed this: that he was part of a chosen elect -- chosen by whom is unclear, since he was not a religious man -- whose responsibility it was to decide how the wealth of society could be best and most wisely allocated. He was not the first or the last to hold such a belief. It is one of the enduring contradictions of American democracy that on the one hand we believe in rule by popular vote, yet on the other we have acquiesced in the formation of a ruling class whose power comes not from the vote but from the pocketbook. Carnegie, who so passionately believed in America and its institutions that he was known as "the Star-Spangled Scotchman," not merely saw no contradiction but believed that it was natural law and that he had been naturally selected.

Carnegie formulated a "gospel of wealth," relying heavily on Spencer, that rebutted "protests against the unequal distribution of wealth by arguing that the common good was best served by allowing men like himself to accumulate and retain huge fortunes. The more wealth that landed in wise hands, the more that could be given away -- wisely -- by the retired capitalist acting 'as trustee and agent for his poorer brethren, bringing to their service his superior wisdom, experience, and ability to administer, doing for them better than they would or could do for themselves.' "

He was as good as his word. Whether the decisions he made were wiser than those that would have been made by an elected government is at least debatable, but the hundreds of libraries built by this man who loved to read enriched the nation incalculably, and his other benefactions similarly made the country a better place. He did himself no honor when he remained silent as his company called in "a private army of detectives to battle its own employees" in the bloody, infamous Homestead Strike of 1892, and the incredible luxury in which he lived with his beloved wife and daughter scarcely suggested sacrifice on his own part, yet on the whole he was honorable and public-spirited. Far more wealth came his way than any human deserves, but he did far better by his good fortune than most others similarly blessed.

Copyright 2006, The Washington Post. All Rights Reserved.