In Union There Is StrengthIn the 1840s, Philadelphia was poised to join the ranks of the world's great cities, as its population grew, its manufacturing prospered, and its railroads reached outward to the West. Yet epidemics of riot, disease, and labor conflict led some to wonder whether growth would lead to disintegration. As slavery and territorial conquest forced Americans to ponder a similar looming disunion at the national level, Philadelphians searched for ways to hold