Harry S. Truman (08/05/1884 - 26/12/1972) was the 33rd President of the United States of America. As Franklin D. Roosevelt's Vice President, Truman succeeded him to the presidency on 12th April 1945, after Roosevelt died only three months into his fourth term in office. One of the most notable decisions Truman made during his leadership was to order the nuclear bombing of Hiroshima and Nagasaki in Japan. Thus President Truman's influence in Watchmen is huge. With its back drop set firmly in the midst of an ever escalating nuclear showdown between the Soviets and the U.S, Truman represents the decisive nuclear might of the U.S.
KT-28s, or Katies, are a fictitional psychoactive drug in Watchmen. Later on in the novel, Dr Manhatten states that he can synthesize limitless amounts of lithium which would lead to advances in technology. Lithium is also used as a drug in psychiatric treatment and the term KT-28, which sounds more like an official pharmaceutical name, implies a legitimate drug which has somehow found its way onto the streets.
Controversial government legal bills aimed at controlling the actions of super-heroes are not a new concept to comic book story lines. In the Marvel Universe, the Superhuman Registration Act required super-heroes to be registered with the government and to have an official ID which legally granted them the power to enforce the law. Watchmen is slightly different in that none of the costumed crusaders, apart from Dr Manhatten and to some degree Captain Metropolis, actually had any super powers. They were just vigilantes who dressed up and got together in order to return law and order to the streets of New York. Their existence led to Police strikes and a huge riot on the streets. So the Keene Act was introduced to outlaw vigilantism the only exception being two government sponsored individuals, Dr Manhatten and The Comedian.