The site is a Scheduled Ancient Monument,[1] although only the mound remains.

It was built shortly after the Norman conquest as a motte castle by Roger of Poitou.

It was recorded in the Domesday Book in 1086 as having attached to it: six burgesses, three 'radmen' (riding men), eight villeins and four neatherds (cattle keepers).

[2] When Roger built Lancaster Castle, Penwortham declined in importance.

In the early 13th century Randolph de Blundeville, Earl of Chester and baron of Lancaster, held his courts in the castle, but soon after the castle fell into disrepair.