Before the Ha'penny Bridge was built, in 1816, there were seven ferries that allowed to cross the Liffey, linking Northern and Southern Dublin. These ferries were the only option to cross the river. As they were in a bad condition and it was decided that a bridge should be built to allow crossing the river.
The company who built the bridge was granted the right to charge a toll from anyone crossing it for 100 years. Initially, the toll charge was half a penny, on any direction, which was the charges of the ferries that this bridge was replacing. There were also turnstiles (gates) on either end of the river, where the toll was charged.
The charge was dropped in 1919.