It is one of the earliest iron bridges in Ireland and Britain, constructed as a pedestrian bridge by William Walsh and John Claudius Beresford.

William Walsh was the lessee of the Bagnio river ferry. He replaced the ferry with the pedestrian bridge which was most likely manufactured by Coalbrookdale Works in Shropshire, England and brought to Ireland by sailing ship.

The bridge spans 42 metres across the river Liffey between Liffey Street Lower on the north side and Merchant's Arch on the south side.

The Ha'penny bridge was opened to the people of Dublin on 19th May 1816 and was toll- free for ten days. After that all users were charged a ha'penny toll to cross the bridge and that toll existed until the turnstiles were removed on 25th March 1919 and passage was declared free to the public.

The bridge has had many different names since May 1816. Originally it was known as the Wellington bridge but it has also been known as the Triangle bridge and the Metal bridge. In 1836, when the first Ordnance Survey was conducted, it was called the Liffey bridge and that is still its official name. However, to Dubliners, it has been and probably always will be known by association with the toll, as the Ha'penny bridge.