Which preposition to use with mostyn

in Occurrences 1%

Five Irish regiments, the first fruits of the cessation in Ireland, arrived[a] at Mostyn in Flintshire; their reputation, more than their number, unnerved the prowess of their enemies; no force ventured to oppose them in the field; and, as they advanced, every post was abandoned or surrendered.

Which preposition to use with  mostyn