On the hillside along First Avenue in Bethlehem lies a mass of graves belonging to men whose blood was among the first to water the tree of liberty. The graves lay under houses and sidewalks. Their names are forgotten to history, but their collective sacrifice is not. The Bethlehem Tomb of the Unknown Soldier, an easily missed landmark on First Avenue, serves as both their grave and memorial. This Independence Day marks 250 years since the natio…