Which locomotive is preserved as the oldest surviving steam locomotive in the world?

Puffing Billy is preserved as the oldest surviving steam locomotive in the world.

Built in 1813–1814 by William Hedley, Jonathan Forster and Timothy Hackworth, Puffing Billy worked at the Wylam colliery near Newcastle upon Tyne in England. It hauled coal wagons on wooden and later iron-edged rails.

The locomotive used smooth wheels on smooth rails, rather than the rack-and-pinion system used by some earlier industrial locomotives. Its low-pressure design and broad wheels suited the colliery’s relatively level railway.

Puffing Billy is now displayed at the Science and Industry Museum in Manchester. It is often confused with Stephenson’s Rocket, but Rocket was a later 1829 locomotive built for the Rainhill Trials and is not the oldest surviving steam locomotive.