Sir John O'Shanassy (1818–1883) arrived in the Port Phillip District from Ireland in 1839. He briefly served on the fledgling council of the City of Melbourne in 1846, before being appointed to the Legislative Council after the separation of the Port Phillip District from New South Wales in 1851.
O'Shanassy was appointed a commissioner to the inquiry into the goldfields on the eve of the Eureka rebellion in November 1854, and spoke for law and order on both sides. His subsequent tour of inspection, accompanied by fellow commissioners, resulted in a report vindicating the miners' stance over their grievances.
O'Shanassy's calm commonsense was considered an asset to his political ambitions and he served as Premier on three occasions between April 1857 and June 1863. O'Shanassy was also a Trustee of the then Melbourne Public Library and the founder of the St Patrick's Society in 1845. In 1859 the society's committee, in a gesture of appreciation, commissioned this portrait.