It was founded in 1641.
Unitarians believe in the Unity or unipersonality of God, as opposed to the doctrine of the Trinity - hence the name 'Unitarian'. Unitarianism only became legal in 1813 but was particularly influential in the 19th century.
This site provides historical information about churches, other places of worship and cemeteries. It has no connection with the churches etc. themselves. For current information you should contact them directly.