The Shire Hall, Monmouth, Wales, is a prominent building on Agincourt Square in the town centre. It was built in 1724, and was formerly the centre for the assize courts and quarter sessions for Monmouthshire. The building was also used as a market place. In 1839–40, the court was the location of the trial of the Chartist leader John Frost and others for high treason f…The Shire Hall, Monmouth, Wales, is a prominent building on Agincourt Square in the town centre. It was built in 1724, and was formerly the centre for the assize courts and quarter sessions for Monmouthshire. The building was also used as a market place. In 1839–40, the court was the location of the trial of the Chartist leader John Frost and others for high treason for their part in the Newport Rising.