PITTSBURGH — On a clear, warm summer evening here in July 1860, nearly 10,000 young men poured into what was then Allegheny City’s Diamond Square from the doorsteps of their different organizing clubs, all in an effort to throw their support behind the men who were running locally as officers for the newly formed Republican ticket in this booming industrial region.

Brass bands played, filling the air with music. So did the spectacle of warm, flickering light as the orderly parade of men carrying brightly illuminated torches joined together at different intersections on their way to the outdoor meeting. The local reporter for the then-Pittsburgh Gazette noted in its story that “the crowd was so dense our reporter could not catch everything that was said” by the newly elected officers of the party.