The City Union Railway Bridge was opened in 1899 and was the first of the permanent Clyde Bridges to have a steel superstructure.
In 1900 the railway system was still expanding in Scotland with keen competition between the big companies.
The two railway bridges across the Clyde were struggling to cope with traffic demands and the City Union Railway Bridge opened in 1899 in response to the demand to carry four tracks into St Enoch Station.