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.

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.

Within ten days of the First Fleet arriving in Australia, records had been made of "The Flats", the extensive tidal wetlands at Homebush Bay.

In 1807, John Blaxland acquired 520 hectares of land, reserving the original grants of Waterhouse, Shortland, Archer and Haslam.

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 younger brother, Gregory Blaxland of Blue Mountains crossing fame committed suicide a few years after his death.

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.

[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.

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 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.

[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.

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.