Number one in industry billings from 1922 to 1972, the J. Walter Thompson agency redefined the advertising industry and transformed the business of media in America. Founded in New York City as Carlton and Smith in 1864, the agency was originally a broker of advertising space in religious journals. The agency hired its namesake, James Walter Thompson, in 1868. Thompson purchased the agency from William James Carlton in 1877, renamed it after himself, and rapidly positioned it as the exclusive seller of advertising space in many leading American magazines.

Most large magazines had existed on subscription and newsstand revenue alone. To create a market for ad space, Thompson persuaded reluctant publishers—who feared advertisements would tarnish their images—to accept advertising in their pages. Thereafter, America's largest magazines relied on advertising as their largest source of revenue, increasing the import of the composition of a publication's readership, and its...