The first London Bridge was a wooden structure built by the Romans, not long after they founded London. This bridge stood a little to the east of the present London Bridge. Here, the Thames was narrow enough to bridge, but still deep enough to handle large vessels.
The wooden bridge was damaged and destroyed many times, most notably by the forces of King Olaf of Norway in 1014. Olaf was assisting King Ethelred in his fight against the Danish invaders camped at Southwark. This is probably the source of the rhyme London Bridge is falling down.
The first stone bridge was started in 1176. It lasted until 1832. Until the middle of the 18th century, it was London's only link with the south bank. The bridge was not only a crossing: there were many shops and houses on either side.
By the end of the 18th century, the bridge could no longer cope with London's traffic. Eventually, a new London Bridge was built to the designs of John Rennie, the great civil engineer and builder of the Waterloo and Southwark Bridges. Although Rennie died in 1821, his son supervised the construction of the bridge, which opened in 1831.
Rennie's London Bridge served the City well for over a century. It was widened in 1902, but finally dismantled in the 1960s. The newest London Bridge opened in 1972.