A hundred years ago, in the autumn of 1918, the Great War was dragging on, so Philadelphia threw a parade to raise morale and sell war bonds called "Liberty Loans." The parade highlighted any available soldiers and sailors, plus the many homefront organizations supporting them. The spectacle would end with a concert conducted by John Philip Souza himself.
When the Fourth Liberty Loan Drive parade stepped off on September 28, some 200,000 people jammed Broad Street, cheering wildly as the line of marchers stretched for two miles. Floats showcased the latest addition to America’s arsenal – floating biplanes built in Philadelphia’s Navy Yard. Brassy tunes filled the air along a route where spectators were crushed together like sardines in a can. Each time the music stopped, bond salesmen singled out war widows in the crowd, a move designed to evoke sympathy and ensure that Philadelphia met its Liberty Loan quota.
But aggressive Liberty Loan hawkers were far from the greatest threat that day. Lurking among the multitudes was an invisible peril known as influenza—and it loves crowds. Philadelphians were exposed en masse to a lethal contagion widely called “Spanish Flu,” a misnomer created earlier in 1918 when the first published reports of a mysterious epidemic emerged from a wire service in Madrid.
Within a couple of days, the hospitals started filling up and people were dying. The entire city was shut down. Read how Philadelphia (and other American cities) reacted to the Spanish flu at Smithsonian.