The halt was constructed so passengers could view the Craven Fault geological site.
The area is designated a Site of Special Scientific Interest and can also be viewed from the railway line itself.
The extension was built largely by volunteers and other organisations who helped out at different stages of the project.
Holywell Halt had never previously existed when the line formed part of the national rail network.
The Holywell Halt site is located right next to the A59 main road to Harrogate.