James Mackay was born in 1804 in Aberdeen, Scotland, the second son of Alexander Mackie and Elspet (née Davidson).

[1] Though his father was the owner of a large shipping company in Aberdeen, James reinvented himself as being born and bred a highlander, which is a likely reason for him assuming the name Mackay.

[5][6] He had studied political economy and free trade principals under John Ramsay McCulloch, which he claimed meant that he supported all measures which had a progressive tendency.

Politically, he participated in committees and actively supported liberal causes such as the passing of the Reform Bill, which gave greater suffrage to common people.

[9] Before leaving, Mackay commissioned a painting which portrays the family as highlanders departing Scotland in tartans and travel attire, stocked with sheep, calves, poultry, ploughs and other accoutrements required for starting a new life in a distant land.

[17] Mackay is noted for his support of the Acting Governor, Robert Wynyard, who argued that it was not possible for Parliament to assume responsibility for governing New Zealand without royal assent.

Mackay, part of the minority who supported Wynyard, attempted to bypass this tactic by presenting a copy of The New Zealand Gazette which contained the prorogation order, shouting "you are no House, you are prorogued!".

Mackay managed to escape, and (in the words of a contemporary) "beat an honourable retreat over the rail into the stranger's gallery, waving defiance to his assailants with his trusty umbrella."

James junior became an Assistant Native Secretary in 1857, and from 1859 to 1860 purchased Kaikōura and the West Coast from Māori on behalf of the General Government.

[24][25] He spent his later years farming, and though still taking an active interest in local politics, he was reluctant to re-enter public office.