Blog was revised and expanded on 1/24/2018
There is currently no bridge at Polk Street across the South Branch Chicago River. At various times there have been five bridges at this site. The crossing goes goes from east to west (800 South; 300 West) 2.6 miles from the river mouth.
The first bridge opened in 1855. It was a pontoon turntable swing wood hand operated. This was the former Clark Street Bridge. It was refurbished for Polk Street.
Contractors were:
Design: John Censor
Construction: City Superintendent of Streets
Construction costs are unknown. Bridge was removed in 1856.
The second bridge opened in 1856-7. It was a pontoon turntable swing wood hand operated.
Contractors were:
Designed: Unknown
Construction: Unknown
Construction cost were $5,000. The bridge was removed In 1869.
The third bridge opened in 1869. It was a swing wood and iron truss center pier swing bridge. It was hand operated. It was 154 feet long and 31 feet wide.
Contractors were:
Designer: Fox and Howard
Construction: Fox and Howard
Construction costs were $36,595. The bridge was destroyed in the Chicago Fire Of 8–10, 1871.
The fourth bridge opened on June 17, 1872. It was an iron tubular swing bridge.
Contractors were:
Design: Unknown
Superstructure Contractor: King Iron Bridge Company
Substructure Contractor: E. Sweet, Jr Company
The bridge was removed in April, 1907.

5th Polk Street Bridge
The fifth Polk Street Bridge opened on September 9, 1910. It was a Strauss Trunnion bascule electric powered bridge.
Contractors were:
Design: Strauss Bascule Bridge Company
Superstructure Contractor: Standard Construction Company
Substructure Contractor: J.J. Gallery
The bridge was closed and removed in 1972.

Remnant of Polk Street Bridge

Area of Polk Street Bridge over South branch Chicago River

Area of Polk Street Bridge

Area of Polk Street Bridge

Area of Polk Street Bridge

Area of Polk Street Bridge
Photos added 4/12/2018