"We need to fix our dysfunctional political system and get unaccounted money out of it, once and for all, even if that takes a constitutional amendment," Hillary Clinton said at Kirkwood Community College in Iowa Tuesday. Michael B. Thomas/AFP/Getty Images hide caption

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The Alfred P. Murrah Federal Building was "literally right up against the road so it was extremely vulnerable," said architect Barbara Nadel. One of the government's first responses was to close a two-block stretch of Pennsylvania Avenue in front of the White House. AFP/AFP/Getty Images hide caption

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