This article relies largely or entirely on a single source. (April 2018)
Rankin was born in Montreal in 1816, the son of Irish immigrants. He ran away from home and became a cabin boy. In 1835, he returned to Canada, then qualified as a surveyor and moved to the Windsor area. In 1837, he smuggled an escaped slave from Ohio to Upper Canada.
He served in the militia during the 1837 Rebellions. In 1843, with nine Ojibwas, he toured Britain with a "wild west show" that appeared before Queen Victoria. In 1844, he returned to Canada. In 1846, he discovered a large copper deposit at Bruce Mines; he sold his share to a mining company in Montreal.
In 1851, he ran for a seat in the Legislative Assembly in Kent but was defeated by George Brown. He was elected to the 5th Parliament of the Province of Canada in Essex in 1854. He was implicated in an 1857 scandal involving the construction of a new railway line in southwestern Canada West; Rankin was defeated in the election that followed. Shortly after that, he helped launch successful copper mining operations along Lake Superior and Lake Huron.
In 1861, he was elected again in Essex. Later that year, he attempted to raise a regiment of Canadians, the 1st United States Lancer Regiment, to serve in the Union Army during the American Civil War.
He was arrested under the Foreign Enlistment Act and forced to resign from the Union Army; in 1863, his election was declared invalid. He was elected again in the general election of 1863. He was a strong supporter of the forming of a Canadian Confederation but did not win a seat in the election held in 1867 for the 1st Canadian Parliament. He died in Windsor in 1893.