Westport House in Westport, County Mayo, Ireland, was the ancestral seat of the Marquesses of Sligo up until July 2014. It was built by the Browne family in the 18th Century, near the site of an O'Malley castle. The architects were Richard Cassels, who built (1730) the east section of the house facing the town, and later James Wyatt, who built the other three façades to form a quadrangle. Later the quadrangle was filled in with a grand staircase. North and south wings were added to the designs of Benjamin Wyatt. The south wing, which contained a library, was burned soon after it was built due to a defect in the heating system.