Who is J.P. Morgan from Reminiscences of a Stock Operator and what is their importance?

J.P. Morgan is a legendary businessman and banker, one of the richest and most powerful men of the time. He makes much of his money in steel and railroads. Livingston recounts an episode when Morgan single-handedly staves off a financial panic on Wall Street by personally ordering major banks to dip into their reserves and make money more freely available. In another story, a salesman extols his superior sales ability by saying he has not only gotten in to see but even sold an entire set of books to J.P. Morgan.