In the vast archive of American tragedy, few objects carry a weight as silent and as heavy as a shard of glass. Housed not in a public museum but in the secured climate-controlled vaults of the National Archives in Washington, D.C., lies a piece of the windshield from the 1961 Lincoln Continental limousine that carried President John F. Kennedy through Dallas on November 22, 1963. To the casual observer, it is merely a cracked composite of laminated silica. But to a nation, it is the “Kennedy Glass”—a physical fracture in the American psyche, a transparent witness to history that has become an opaque symbol of enduring doubt.