The contingency plan developed after 9/11 also had its first real test that day: The Senate convened in a pro forma session at one of several secure locations selected to house the chamber should the Capitol be uninhabitable.
Still, officials say, perhaps the most significant changes are those that the public might never know about: classified programs to thwart conventional, chemical, biological and even nuclear weapons and suicide bombers.
“There’s so much of what goes on [around] the Hill that is classified,” said former Senate Sergeant-at-Arms Bill Pickle, who served from 2003 to 2007. “The biggest changes are the ones that are not the most readily apparent, and that’s the way it should be.”
Rep. Elijah Cummings, D-Md., right, hugs Harold Schaitberger, General President of the International Association of Fire Fighters, after the Congressman spoke at the IAFF's Legislative Conference General Session at the Hyatt Regency on Capitol Hill, March 9, 2015. The day featured addresses by members of Congress and Vice President Joe Biden.