Two old steamer trunks sit in the rare-book room at the Virginia Historical Society, looking worn and forlorn. The smaller one was once red but the paint has faded to a dull rust. The larger one is brown with a piece of tin patching a hole in the top. On one side, a name is stenciled: "M. LEE." That's Mary Custis Lee, Gen. Robert E. Lee's adventurous eldest daughter. In 1917, she stored these wooden trunks in the "silver vault" in the basement of Burke & Herbert Bank & Trust in Alexandria. A year later, she died at the age...