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1739-50 The first Westminster Bridge was built having been designed by the Swiss architect Charles Labelye
1854 Construction started on the replacement bridge. Designed by Thomas Page. Overall length of 826.8 ft and a width of 88 ft, it is a seven-arch wrought iron bridge with Gothic detailing by Charles Barry.
The ironwork of the bridge was made by Messrs. Cochrane, of Woodside, near Dudley.
1862 May 24th The new bridge opened for traffic.
"...The north footway of the new Westminster Bridge was opened to the public at 9 o'clock on Tuesday morning, and affords a spacious promenade. It is 14ft. in width, laid in the Stamford hard-burnt terracotta tiles, 12in. square, and bordered on the edge next the carriage-way by a curb of the red granite of the Isle of Mull. The temporary footway and timbering on the lower side of the bridge is being rapidly removed, so that the details of the whole structure will soon be open to public..." 
"The Westminster Bridge was opened for traffic in 1862. It was built by Thomas Page, and work on it was begun in 1859. There are seven arches, each formed of seven ribs, which are of cast iron nearly up to the crown, where to avoid danger from the concussion of heavy loads they are made of wrought iron. The span of the arches varies from 96ft. to 120ft., and they have a height of from 16ft. to 20ft. above high water level. The design of the bridge was made to harmonise, as far as possible, with that of the adjoining Parliament buildings. Despite tho greatly increased weight and speed of the traffic using the bridge, we believe the structure will be found to be very well preserved."
1924 "On Tuesday afternoon last, precisely at three o'clock, all traffic was held up at either end of Westminster Bridge for a period of five minutes. This interval was sufficient to allow the engineers of Messrs. Rendel, Palmer and Tritton to take reading of the loading conditions of the bridge when free from traffic, while the effect of the sudden renewal of normal traffic was also noted. The information gained during this test will serve to complete the work of testing the bridge, which has now been in progress for about five months. The report on the bridge, which is being prepared by Messrs. Rendel, Palmer and Tritton for the London County Council, is now, we learn, well advanced and will be presented shortly."