At the time of Griffiths Valuation in the early 1850s, Williamstown House was leased by William Allen from the Edgeworth estate, when it was valued at £10. A much smaller building appears at the site on the 1st edition Ordnance survey map. The National Built Heritage Service suggests the existing Williamstown was built c.1847. It is still in use. In the 1870s William Allen was recorded as the owner of almost 200 acres in County Longford.
Williamstown House [Longford] (National Built Heritage Service)
