Old OK 18 Squirrel Creek Rainbow Arch Bridge, Pottawatomie County.

The only rainbow concrete arch bridge left in Oklahoma (only two were ever built) stands between Shawnee and Tecumseh on an old stretch of what used to be OK 18 in Pottawatomie County.

This bridge was built in 1917 and is 67 feet in length. State records claim that convict labor from the state pen in McAlester was employed to build this bridge.

Above, a view through the bridge looking to the north. The bridge deck is just 15 feet wide. The bridge is constructed entirely of reinforced concrete, except the horizontal guard rails, which are steel pipes coated with concrete to look like they are cast concrete.

Below, a side view of this very unique and historic structure. Generally, when people think of Rainbow Arch, or Marsh bridges, they think of Kansas, where large numbers of this type of bridge were built in the teens and 20's.

Below, a view of the underside of the deck. Each of the transverse ribs connects to the lower chord at a point where it is intersected by a vertical tie.