They are, from front to back, the Center Street Bridge (low-level swinging, built 1901); the Superior Viaduct (high-level swinging, built 1878); the Main Avenue Bridge (high-level stationary, built 1939); and the Cuyahoga River Bridge #1 (low-level vertical lift, built 1956). And the picture was taken, of course, from the Detroit-Superior Bridge (high-level stationary, built 1917).