India, Oct. 29 -- You have probably walked down a leafy street without giving a second thought to who planted the trees. On 16th Street in Washington, D.C., the answer is a city remembering the people it lost in World War I. The Association of the Oldest Inhabitants of the District of Columbia notes the city planted the first of 507 Norway maples there on May 30, 1920, as a memorial to its war dead. Each tree was dedicated to a local war casualty. The idea was simple and kind. But a century later, those trees have moved on to a surprising second act.

The first dedication was on Memorial Day, and several people in the crowd were veterans. The same document says that Assistant Secretary of War Benedict Crowell and D.C. Commissioner Louis B...