Irving Vermilya, 1HAA, later W1ZE, became the first licensed amateur in the USA being issued Certificate of Skill #1 and is known for all time as Amateur Number One. A number of other amateurs followed suit and rather than seeing amateur radio die out as the Law's authors obviously intended, amateur radio began to flourish with a combination of adopting new technology (Edwin H. Armstrong invented the regenerative receiver in September 1912) for reception and later transmitting (CW emissions became feasible after the World War) along with organizing message relay routes. Amateurs led the way finding that the wavelengths shorter than 200 meters were not useless through the new technologies and, by the early 1920s, a declining solar cycle that enabled communications not only for transcontinental paths, but intercontinental as well.
A century later we enjoy this hobby of amateur radio precisely due to the unintended consequence of a law designed to kill amateur radio that did not state its intention exactly and instead allowed it to live and thrive for 15 years! In 1927 more comprehensive radio legislation was enacted and in 1934 the Communications Act created the FCC that we know today.
For more information visit the United States Early Radio History site by Thomas H. White. Thomas' site is not limited to amateur radio, however, and is quite comprehensive on a lot of radio topics. The ARRL publication, 200 Meters and Down by Clinton B. Desoto documents much of the early amateur radio history. An article by David Newkirk, ex WJ1Z, now W9VES, The Coming of The Law (available to ARRL members), published in the November 1993 issue of QST also documents the forces behind the enactment of the Radio Law of 1912 and how radio amateurs responded to it. The December 2012 issue of CQ has The Radio Act of 1912: A Century of Radio Regulation and Licensing by Rich Moseson, W2VU, providing another perspective on this red letter day. Certainly, more articles on this topic have been published over the years and make for good reading.
As of December 13, 2012 amateur radio will officially be 100 years old complete with examinations and licenses. Happy anniversary!