A couple of years ago I was lucky enough to find a copy of the Art Directors Club's 51st Annual of Advertising, Editorial and Television Art & Design (pictured). Released in 1971, this was the first Annual to feature inductees into the organization's Hall of Fame. The names inducted that year include legends Lester Beall, Paul Rand, and William Golden.
In explaining their decision to create the hall, the ADC Board of Directors said: "This year we inaugurate the Hall of Fame. The nomination and election each year of these people will help to educate and inform not only the young people entering our business, but we hope will serve as an inspiration to all of us. In their hands, advertising and graphic communication [becomes] an art form."
Each inductee -- a rather long list now -- is accompanied by a thorough, well-written biography. When taken together these entries are a kind of classical education in modern American design. And although it doesn't get much publicity, the the complete Art Directors Club HoF membership roster is available online, including the bios. Wow.
It'd be hard to overstate the value of a resource like this. Far more than, say, Wikipedia, it is the place to go to learn about who these people were, how they worked, and why they matter.
Get started over there with George Lois, Alvin Lustig, or the aformentioned Lester Beall and Paul Rand.
Then, be prepared to get lost for a day or so.