In the Phoenix area, besides the Center Street Bridge, which opened on Central Avenue in 1911,[1] it was one of two crossings at the Salt River for some time.

Due to monsoon storms heavy rains would fall, and washes and street runoff emptied into the river.

At such times the unbridged crossing was closed, and the bridge was opened to north- and southbound traffic, one lane in each direction.

In 1980 all but two of the bridged crossings on the Salt River were closed for safety reasons (principally erosion of the approaches) due to severe flooding.

The Old Mill Avenue Bridge was listed on the National Register of Historic Places in 1981, celebrating the 50th anniversary of its opening.

This allowed for two lanes to travel in each direction (north and south), instead of the previous single, two-lane bridge.

With two lanes now running in each direction no matter the weather, monsoon storms and releases from dams no longer lead to traffic obstructions.

On September 21, 2018, the Mill Avenue Bridges were designated as part of Historic U.S. Route 80 by the Arizona Department of Transportation.