Portus was born at Black Creek, near Morpeth, the son of a mill owner John Portus and wife Elizabeth. He was educated at a local school under a Mr. Carmichael, and travelled to Europe at 21 for the 1855 Paris Exhibition, also visiting Canada and the United States. Upon his return, he worked as an engineer alongside his brother at Raymond Terrace. He was also a director of the Maitland and Morpeth Railway Company and the Hunter River New Steam Navigation Company. In May 1861, he was one of Charles Cowper's 21 appointments to the New South Wales Legislative Council, however did not take his seat in the council.