Petty gained possession of the three baronies of Iveragh, Glanarought and Dunkerron in County Kerry. He soon became a projector, developing extensive plans for an ironworks and a fishery on his substantial estates in Kerry. Although he had great expectations of his application of his scientific methods to improvement, little of practical consequence came of these. He started by applying his political arithmetic to his own estates: he surveyed the population and livestock, to develop an understanding of the lands potential. The ironworks was established in 1660.