As the nation's TV viewers know from watching many an open Cadillac or caissonmake the trip, Pennsylvania Avenue in Washington, D.C., has both grandeur and grubbiness. As it stretches toward the Capitol, the stalwart neoclassical façades of federal buildings rise evenly on the right. But on the left side is an uneven collection of old hotels, decayed storefronts vacant above the first floor, and dreary parking lots.
Yet, as conceived by George Washington, who suggested it to the capital's original planner, French Engineer Pierre Charles L'Enfant, Pennsylvania Avenue was to be a symbolic "axis of the nation," balancing democracy at...