He emigrated to the British Province of South Australia with his wife in 1839 and represented the City of Adelaide in the House of Assembly from 1860 to 1862 before becoming a member of the Legislative Council from 1866 to 1867.
Parkin was a benefactor of the South Australian Congregational Church and founded many religious philanthropic efforts.
The Australian Dictionary of Biography described him as "quiet and conscientious" and he became respected for his "quaint, humorous, but intelligent addresses".
Parkin College was founded with an endowment of £8,000 and 4,160 acres of land near Darwin, Northern Territory, and left another £16,000 in his Will.
He married twice: on 16 May 1832 to Sarah Mary Carill (c. 1814 – 23 March 1871) and on 28 February 1872 to Ellen Stonehouse (died 13 May 1925), daughter of Rev.