From 1844 to 1859 he worked for various Ontario Newspapers before coming out to Vancouver Island.
His daughter Elizabeth was one of the fatalities of the 1875 SS Pacific wreck at the entrance to the Strait of Juan de Fuca.
In October 1865 he bought a half interest in the British Columbian in New Westminster.
It was when he owned the News that he was sued successfully by Amor de Cosmos for libel.
De Cosmos hired McMillan as a printer and then journalist and finally in 1871 as editor in chief of the Standard.