Blaxland was born in Kent, the eldest son of gentleman farmer John Blaxland and Mary, née Parker, of Fordwich, Kent, England. He was the older brother of early Australian explorer Gregory Blaxland. His father died when he was eleven^[1] and the family moved to Canterbury where he and his brother were educated at The King's School. In 1787 he joined the army and rose to become a captain. He resigned his commission in 1792 and returned to manage the family estates at Newington, Kent. He was married twice: to Sarah Davies from 1794 until her death in childbirth in 1795, and to Harriet, daughter of Jean Louis de Marquett (a merchant of Calcutta and a former guard of Louis XVI), from 1797 until his death in 1845. He and Harriet had four sons and six daughters.^[2][3]

In 1805 John and his younger brother Gregory were persuaded by Joseph Banks to emigrate to Australia. Blaxland made a good bargain with the English government which agreed that if he brought £6000 to the colony he would be granted 8,000 acres (32 km²) of land, the labour of 80 convicts who would be fed for 18 months by the government, and a free passage for himself, his wife, children and servants.^[2]

Gregory was the first to sail to New South Wales while John remained to sell the family estate in Kent. John reached Sydney on 4 April 1807, having, in conjunction with Hulletts brothers, of London, built The Three Brothers, a ship of 252 tons, carrying eight guns and a crew of 21 to bring himself, his wife, and four daughters, a governess, two female servants, a bailiff, a carpenter, a man for agricultural purposes and a boy to this land, Oliver Russell being the master.^[4]

He arrived with instructions to Governor Bligh to give him various concessions in place of the free passage. Bligh was no more helpful than he thought necessary, but Blaxland obtained cattle from the government herd, and started a dairy in Sydney, and also sold meat and vegetables.

Blaxland did a very useful piece of work in reducing the prices of these necessities, but Bligh insisted that he should go in for agriculture as well as grazing. He antagonized Blaxland, who joined in the deposition of Bligh in January 1808, but Blaxland could not get the concessions he wanted from Colonel Johnston.

Within ten days of the First Fleet arriving in Australia, records had been made of "The Flats", the extensive tidal wetlands at Homebush Bay. Between the years 1788 and 1831, blocks of land ranging from 100 to 10,000 acres (40 km²) were given out to the first European settlers by dividing up the Wanng-al clans' land. These land grants were inked in on County of Cumberland maps, with names of owners and land granted clearly indicated. In 1807, John Blaxland acquired 520 hectares of land, reserving the original grants of Waterhouse, Shortland, Archer and Haslam. He named the estate Newington after his family estate in Kent, England.^[5] Blaxland established a series of salt pans on the banks of the Parramatta River and by 1827, was producing 8 tons of salt each week for the Sydney market. Blaxland also established a tweed mill, limekiln and flourmill. In 1843, Blaxland mortgaged the property to the Australian Trust Company. After he died in 1851 the Trust Company sold the property to John Dobie to recover the mortgage. The Blaxland family re-purchased the estate from Dobie in 1854 but offered it as security against a large loan. The property was transferred to the Official Assignee of the Insolvent Estate of Edward James Blaxland in 1860 and subsequently leased to the Methodist Church, who established Newington College on the estate. The building is now listed on the Register of the National Estate.^[6]

Blaxland then decided to return to England. Bligh, however, succeeded in getting him arrested at Cape Town and taken to London. After three years in London he obtained a letter to Macquarie directing that the original agreement should be carried out. But Macquarie was obsessed with the idea that the land grants were for the purpose of growing grain and put various obstacles in his way.

Blaxland returned to Sydney on 27 February 1818, on board the Laurel. With him was Mak Sai Ying, the first known Chinese man to settle in Australia. Mak Sai Ying was later to negotiate land deals favourable to Blaxland, while working as a carpenter, until 1821.

However, in the 1820s, under Governor Brisbane, Blaxland obtained good land in the Nepean (800 acres called "Grove Farm" where he had built a weir and brewery where barley and English soft wheat were grown at what became Wallacia) and Hunter Regions as a result of discovering a route to the area. His grant was in the area now known as Broke and by 1830 he had established a mill in the nearby area of Fordwich.^[7] Over the years he was successful as a stock owner. He was a member of the New South Wales Legislative Council from 1829 to 1844 and died at Newington on 5 August 1845.^[8]

Blaxland married twice, firstly to Sarah Davies (who died during childbirth) and secondly to Harriott de Marquett, daughter of Jean Louis de Marquett (a Calcutta merchant and a bodyguard of Louis XVI). He was survived by several sons and daughters from his second marriage. His younger brother, Gregory Blaxland of Blue Mountains crossing fame committed suicide a few years after his death.

Their eldest daughter Harriott firstly married Calcutta merchant Alexander Macdonald Ritchie with whom she bore three children: Elizabeth, Arthur and Alexander. Through her family connections (both maternal and spousal) Harriott spent some time in India and wrote an account of a suti or widow-burning, the account is now in the Library of New South Wales.

Harriott and Alexander's daughter, Elizabeth, married^{[Notes 1]} a Welshman, Charles Boydell, who was a pioneer in the Hunter Valley, in particular, Gresford, New South Wales where he had a property called Camyr Allyn.^[9] Charles' brother William married the daughter of the first Anglican Archbishop of Australia, William Broughton, also an alumnus of the King's School, Canterbury. From Elizabeth's line, descendants married into families such as the wine-making Lindemans. From Arthur's line, descendants married into the British nobility.^{[Notes 2]}

Harriott, as Mrs Ritchie, was the subject of a romantic tryst with French navigator Hyacinthe de Bougainville.^{[Notes 3]} In de Bougainville's account, the navigator was pleasantly surprised to find an Anglo-French speaking family in the colony, connections to Louis XVI and praised Blaxland as a truly English gentleman.

After Alexander Ritchie's death, eldest Harriott married the second Chief Justice of NSW, fellow widower Sir James Dowling, thereafter becoming Lady Dowling. Furthermore, Lady Dowling's father, who was known as a liberal, made Sir James pointed out the difficulties of advancement in the colony for having so close a connection to a "Kentish whig":^[10]

Dowling recognised that his recent remarriage to Harriott Ritchie, a widow, ("the daughter of a most respectable man and worthy gentleman...and an honest upright man...who has the misfortune to be a Kentish whig"), might weigh against him.

Their second daughter, Anne, married Thomas Walker who had considerable holdings in the area now known as Rhodes.

Their eldest son, John de Marquet, who died young and unmarried, was an early explorer and cattle drover who found a passage from Sydney to Cessnock where his family were granted land holdings. Blaxland Arm near the town of Laguna, New South Wales is named after him.^{[Notes 4]}

Eliza Maria, his fifth daughter married Henry William Breton on 3 November 1832.^[11]

Their youngest daughter, Louisa Australia (so named as she was the first of the Blaxland children born in Australia), lobbied the State Government and Sir Henry Parkes to keep the family estate intact and preserved to no avail.

The family's (with the Walker's) extensive documents are held in the archives of the State Library of New South Wales.^[12]

John Blaxland was a keen man of business, anxious to drive a good bargain, and as a free settler was in a stronger position than the emancipists. But he antagonized both Bligh and Macquarie and met with much opposition. In spite of this Blaxland as a pioneer grazier became an important figure as the quintessential 19th century enlightened English gentleman in the early development of Australia.

• Dyer, C.(2009) The French Explorers in Sydney, Santa Lucia: University of Queensland Press.
• Irving, T H (1966). "Blaxland, John (1769 - 1845)". Australian Dictionary of Biography. National Centre of Biography, Australian National University. pp. 117–118. ISSN 1833-7538. Retrieved 3 May 2019.
• Serle, Percival (1949). "Blaxland, John". Dictionary of Australian Biography. Sydney: Angus & Robertson.
• "THE BIOGRAPHER". The Sydney Mail and New South Wales Advertiser. Vol. XXXVI, no. 1216. New South Wales, Australia. 27 October 1883. p. 775 – via Trove.