- Alternate meanings: John D. MacArthur, John R. Macarthur
Macarthur joined the Army as a young man and arrived in Sydney, then a small and isolated penal colony, as a lieutenant in the New South Wales Corps in 1790. This was an undistinguished unit banished to a remote posting, and the quality of its officers was not high. The main currency of the colony was spirits, and the Corps soon monopolised the trade and earned the nickname the Rum Corps.
In 1792 the acting Governor, Francis Grose, appointed him paymaster and inspector of public works, and gave him a land grant at Parramatta, west of Sydney, where he and his highly capable wife Elizabeth farmed successfully. Around this time he developed the idea that New South Wales would be an excellent place to grow high quality wool. In 1794 he imported his first sheep, and in 1796 he was able to import Spanish merino sheep and establish Australia's first commercially successful wool exporting business.
Macarthur quarrelled with successive governors and most of his neighbours, and in 1801 he was sent to England for court martial after being involved in a duel. In England he got the charged against him dropped, and lobbied for support for his wool-growing ideas. The Colonial Secretary, Lord Camden, supported him, and in 1805 he returned to Sydney with authority to establish a large sheeprun south of Sydney, which he called Camden Park.
Wool had great advantages as an industry for New South Wales, which because of its distance from European markets needed a commodity which did not perish during long sea-voyages and which offered high value per unit of weight. Wool was such a commodity, and it had a ready market in England because the Napoleonic Wars had cut English cloth-makers off from their traditional source of quality wool, Spain. The export of wool soon made Macarthur the richest man in New South Wales.
In January 1808 Macarthur was a leading figure in the Rum Rebellion against Governor William Bligh, who had tried to suppress the traffic in spirits, which he believed was ruining the colony. It was Bligh who had famously said to Macarthur: "What have I to do with your sheep, sir? Are you to have such flocks of sheep as no man ever heard of before? No, sir!"
After the rebellion Macarthur resigned his commission to avoid court martial and returned to London, where he remained in exile until 1817. During these years Elizabeth ran Camden Park, and she has as good a claim as her husband to be regarded as the founder of the Australian wool industry.
On his return to the colony Macarthur devoted himself to farming. As well as expanding the wool industry, he established Australia's first commercial winemaker, was a founding investor of the Australian Agricultural Company and the Bank of Australia, and was an early member of the New South Wales Legislative Council. He died at Camden in 1834. His numerous and wealthy family remained influential in New South Wales affairs for many years. As the Macarthur-Onslows they are still wealthy but no longer prominent in public life.