The Chicago River is as mighty as ever in this beautiful vintage photo. In a dazzling feat of engineering, the river’s course was reversed in the 19th century to carry sewage away from the city, and toward the Mississippi River basin. 156 miles long, the Chicago River is spanned by 45 bridges that lift when boats pass underneath. And each year on March 17, its currents run green with dye thanks to the mischievous St. Patrick’s Day tradition.