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.”
Former Sen. Scott Brown, R-Mass., candidate for U.S. Senate in New Hampshire, holds his hand over his heart during the singing of the national anthem as he waits to take the stage for his town hall campaign rally with Sen. John McCain at the Pinkerton Academy in Derry, N.H., on Monday, Aug. 18, 2014.