Philadelphia's Washington Square, a shaded 6.6-acre plot near the nation's birthplace at Independence Hall, has been a focal point of the city's history for more than 300 years. Designated by William Penn in 1683 as an open space, the square served as a potter's field for its first 100 years. The remains of more than 2,000 indigents, soldiers, and yellow fever victims rest beneath its sod. By 1825, the graveyard was closed and the square was redesigned...