The 1.6 km long bridge over the Mississippi was opened in 1929. It was financed by bridge tolls collected on the Missouri side of the bridge keeper's cottage. Route 66 was moved here in 1936.
It owes its name to a chain of rocks in this part of the Mississippi, which badly affected shipping. However, after the water level has been raised by barrages, these are no longer visible. The 22° bend almost in the middle of the bridge is remarkable. This benefited shipping. Due to the incline in relation to the direction of the river, the distance between the supports is ideal in order to take a better alternative course so as not to collide with the water towers located just behind the bridge.
Northbound ships didn't need evasive maneuvers, though, so a bridge running straight across the river was better here. In 1967, the bridge was replaced with a new one a little further north, which now carries I-270.
It rusted away for about 30 years before it was restored and is now open to pedestrians and cyclists again, making it the longest pedestrian bridge in the world. They actually wanted to tear it down in 1975, but the cost of doing so would have been higher than what could have been recovered on the scrap market. What luck from today's point of view.