George Washington's spies used invisible ink during the Revolution. Abraham Lincoln's young cryptanalysts cracked the Confederacy's "Vicksburg Square" cipher during the Civil War. The United States entered World War I after Britain decoded an encrypted message from the Germans inviting Mexico to wage war on America—the so-called "Zimmermann Telegram." In World War II, the Marines' Navajo "code-talkers" were crucial to victories in the Pacific theater.
Because puzzle-solvers and code breakers have long been heroes of American history, we present the Smithsonian Great American History Puzzle. The puzzle is a month-long contest conceived by the puzzle master and "Jeopardy!" champion Ken Jennings. The first person to correctly follow all the clues, avoid all the red herrings and uncover all the secrets will win the grand prize: a free trip to Washington, D.C. and a "Secrets of the Smithsonian" tour (created by Smithsonian Journeys and valued at $10,000) behind the scenes of the world's largest museum and research complex.