Ranfurly was the eldest son of Thomas Knox, 1st Viscount Northland, and the Hon.
[1] Ranfurly was elected a member of the Irish House of Commons for Carlingford in 1776, a seat he held until 1783, and then represented Dungannon between 1783 and 1790 and County Tyrone between 1790 and 1798.
[4] On 18 May 1793 he was commissioned as Lieutenant-Colonel and second-in-command of the newly raised Royal Tyrone Militia.
[5] In 1818 he succeeded his father in the viscountcy of Northland, but, as this was an Irish peerage it did not entitle him to a seat in the House of Lords.
However, in 1826 he was created Baron Ranfurly, of Ramphorlie in the County of Renfrew, in the Peerage of the United Kingdom, which entitled him and his successors to a seat in the upper chamber of parliament.