On the eve of the 250th anniversary of the birth of our nation, the Highmark Mann Center for the Performing Arts travels back in time to the 1876 Centennial Exposition in Philadelphia. The Civil War had ended just over a decade before. But the Long Depression that began in 1873, triggered by overexpansion in railroads, banking, and heavy industry, still held the world economy in its grip. Against this backdrop, the Exhibition was a beacon of hope and pride—and not just for the United States. Some three dozen other countries came to Philadelphia with displays of their own. Between May and November, the City of Brotherly Love, whose population hovered around 750,000, played host to no fewer than 10 million visitors. The 21-acre Main Exposition Building was at the time the largest building in the world. Among groundbreaking technological innovations, the sleek Corliss steam engine gleamed as the icon of industrial potential. In their new oratorio, the librettist Mark Campbell and composer Peter Boyer imagine the intersecting lives of five visitors on a single day. (For some reason, we’re envisioning Ragtime meets Assassins.) Campbell and Boyer’s principals are Mary Dunleavy, Meredith Lustig, Eve Gigliotti, David Portillo, and Malcolm J. Merriweather; Anthony Parnther conducts the Philadelphia Orchestra and the choral ensemble known as The Crossing; Tazewell Thompson directs. —Matthew Gurewitsch