He was born to an Ulster Scots family in County Antrim in what is now Northern Ireland, and emigrated with his widowed mother to Indiana when he was nine years old.

McClure's Magazine published influential pieces by respected journalists and authors including Jack London, Ida Tarbell, Upton Sinclair, Burton J. Hendrick, Rudyard Kipling, Sir Arthur Conan Doyle, Robert Louis Stevenson, Willa Cather, and Lincoln Steffens.

Phillips left to purchase The American Magazine in 1906 and McClure sold his book publishing operations to Doubleday, Page in 1908.

Rudyard Kipling was one writer who rejected McClure's offer of a long-term contract, quoting as justification Ecclesiasticus (Chapt.

Lyon suggests that he had a manic-depressive personality, combining enthusiasm, tenacity, and a remarkable talent for predicting public responses.