After many problems, the original Westminster Bridge was opened in 1750, the first stone having been laid nearly eleven years earlier. No toll was ever charged on the bridge which was paid for by the government. At night it was lit by 32 oil lamps which were replaced in 1814 by gas lamps and electric lighting was installed in 1898.

In 1753 there was apparently a 'great want of proper places to piss in the four corners of the bridge. For the great numbers that piss there cause it to run down to the houses which make it very offensive'. To solve the problem, a basin was installed at each corner of the bridge.

In 1843 attempts were made to strengthen the foundations of the piers that were beginning to sink. The bridge continued to be repaired until it was finally decided to replace it with a new bridge which was built slightly upstream and officially opened in 1862. The bridge consists of seven iron spans and is of double the width of the old bridge. The arches are formed of cast iron ribs with wrought iron flat crowns on each arch. The brick piers and abutments are faced in granite, and the abutments built using some of the Portland stone from the old bridge. Gothic detailing on the cast iron parapets and spandrels incorporates the coats of arms of England and Westminster. The predominant colour of the bridge is green, the colour of the seating in the House of Commons which is located at this end of the Houses of Parliament.

A bronze statue of Boadicea (Boudicca) and her daughters was erected at the north end of the pier in 1902. Boadicea was famous for leading a revolt against the Romans in AD61 during which the city of Londinium was burnt to the ground. At the other end of the bridge stands the South Bank Lion which, from 1837 stood painted red, on top of the Lion Brewery which stood where the Royal Festival Hall now stands. The lion was moved to the bridge in 1966.