BRIEF HISTORY DURING THE SNOW ERA (1813-58)

Westminster Bridge was built in 1738-50 by engineer Charles Labelye following the 1722 design of Colon Campbell.  Until then, local persons who wanted to cross River Thames had to travel some distance east to the London Bridge.  Labelye's bridge had fifteen arches, was built of masonry, and rested on piers. 

By 1837 the Westminster Bridge had deteriorated and major work was done to replace the piled foundation.  Shortly thereafter a parliamentary committee reviewed the situation and recommended even more -- namely that a new, wider bridge be built.  This occurred.  A cast-iron bridge of seven arches was designed and built in the same location by Thomas Page in 1854-62, with limited public access starting in 1860.  Dr. John Snow, who died in 1858, never had the opportunity to cross the new Westminster Bridge although likely he used the older one when visiting Lambeth, Vauxhall or Southwark.  

The 1862 Westminster Bridge is still the current bridge. 

Sources: 

Herring JH. Thames Bridges from London to Hampton Court, with Topographical Descriptions from Best Known Authorities, H.R. Pinder, London, 1874.

Weinreb B, Hibbert C (eds). The London Encyclopaedia, 1993.