At the end of the seventeenth century the Trinitarians were brought to Ilava — an order founded to collect money and buy Christians out of captivity in North Africa and the Ottoman lands. Building of their monastery began in 1692, and in 1694 the upper castle was converted into it. It was the order's first house in the whole Kingdom of Hungary. They lectured on philosophy there and ran a hospital, which for a small town was a serious public service. Between Trenčín and Žilina there were only three monasteries on the entire Váh: Benedictines at Skalka, Franciscans at Pruské, and the Trinitarians here.Koncom 17. storočia priviedli do Ilavy trinitárov – rehoľu založenú na to, aby zbierala peniaze a vykupovala kresťanov zo zajatia v severnej Afrike a v Osmanskej ríši. Stavba ich kláštora sa začala v roku 1692 a v roku 1694 naň prebudovali horný hrad. Bol to prvý dom rehole v celom Uhorsku. Prednášala sa tu filozofia a fungovala tu nemocnica, čo bola pre malé mesto vážna verejná služba. Medzi Trenčínom a Žilinou boli na celom Považí len tri kláštory: benediktíni na Skalke, františkáni v Pruskom a trinitári tu.
