What is "penstrowed"

Penstrowed is a historic Montgomeryshire parish to the west of Newtown, now in Powys. It is situated in the river Severn valley. The founder of the church, Saint Gwrhai was a 5th century saint who is supposed to have been buried in the churchyard. The Penstrowed Quarry was an important source for local stone and was used for building the Caersws workhouse. It was later acquired by Montgomeryshire County Council and a railway siding connecting the quarry to Cambrian main line laid in 1902 and closed in May 1937.