The London Bridge was originally built in the year 50 AD. The wooden construction was replaced with rocks in the 12th century, and then in granite in 1831.
The bridge was deemed too small in 1967, so London authorities decided to build a new, more modern London Bridge.
Each piece of the bridge was meticulously numbered, dismantled, and carried by boat across the Atlantic, through the Panama Canal, and all the way to California. From there, they made it to Arizona by truck.
Sources: Wikipedia and Lake Havasu City