in the late 12th century brought significant changes. By 1235, the invading de Barra (Barry) family had established a castle on the banks of the Castlebar River, around which the town developed. This castle, known as Caisleán an Bharraigh, gave the town its name. The de Barra's stronghold later came under the control of the de Burgo (Burke) family, who faced challenges from other clans and English forces. The castle was located at the end of Castle Street, where the town river is thought to have originally flowed.

In 1586, Sir John Bingham