Carroll Street Bridge, 1960.

Opened in 1889, the Carroll Street Bridge is a rare retractable crossing, one of two in New York City and three (as of 2013) still in service in the United States. It opens diagonally, with its span slowly pulled into a reserved pocket on the Gowanus Canal’s western bank. Bridge openings are now a rare event, but were once quite common. According to the New York Times:

“As recently as the 1990s, the canal was a major waterway for paint factories, oil depots, sand and gravel suppliers, and warehouses alongside it, and the Carroll Street Bridge had to be opened 500 to 700 times a year.”