56 years ago on May 17th, 1968 A second round of protests take place at Columbia University, lasting for five days and resulting in 177 arrests References: Wikipedia
140 years ago on May 17th, 1884 P.T. Barnum leads a parade of 21 elephants across the Brooklyn Bridge
48 years ago on May 17th, 1976 The Roosevelt Island Tram opens for business, becoming the first commuter aerial tramway in North America