 He arrived in Buenos Aires and then travelled to Mendoza and to Chile across the Andes and then to Peru.Once in Lima, he contacted Ambrosio O'Higgins, another Irishman, at that time Viceroy of Perú, who named him Governor of Osorno and put him in charge of the reconstruction works for this southern Chilean town.In this capacity, Juan Mackenna convinced the families of Castro, on the island of Chiloé, to move to Osorno to found a colony there.