Short answers, pulled from the story.
The North Atlantic Treaty was signed on the 4th of April 1949 in Washington, D.C. The signing committee was chaired by U.S. diplomat Theodore Achilles. The treaty came into force on the 24th of August 1949, after all signatory states had completed ratification.
Theodore Achilles produced the first draft, drawing heavily on the Rio Treaty and borrowing language from the Brussels Treaty. Achilles credited John D. Hickerson as the single most important author, calling it a one-man Hickerson treaty. The secret draft was written following talks at the Pentagon between the 22nd of March and the 1st of April 1948.
Article 5 has been invoked only once, following the September 11 attacks on the United States in 2001. NATO Secretary General George Robertson suggested the invocation to Colin Powell, and the North Atlantic Council acted on its own after the U.S. indicated it would not object.
Article 6 limits Article 5 protection to member states' territories in Europe, North America, Turkey, and Atlantic islands north of the Tropic of Cancer. Hawaii was judged in 1965 not to fall within the treaty's geographic scope. The Falkland Islands, being in the South Atlantic south of the Tropic of Cancer, were also outside coverage during Argentina's 1982 invasion.
The Canada Clause is the informal name for Article 2, which Lester B. Pearson pushed to include. It calls on members to develop peaceful international relations, strengthen free institutions, and promote economic collaboration. Pearson's original proposals included a trade council, cultural program, technology sharing, and an information program; only the last two were adopted.
No member state has ever formally withdrawn under Article 13, which requires one year's notice to the U.S. government. France withdrew from NATO's military command structure in 1966 but not from the alliance itself, and rejoined the command structure in 2009. Greece similarly withdrew from the military structure in 1974 and rejoined in 1980.