Thomas Brown, the man with the best claim to be the founder of Lithgow, was born in the Parish of Westerkirk, Dumfriesshire, Scotland, on 24 May 1811, the second in a family of eleven. On 5 June 1838, at the age of 27, he married Mary Maxwell of the nearby Parish of Langbolm.

Three weeks after their marriage Thomas Brown and his wife sailed from Liverpool for Sydney on the Laura, a barque of 330 tons displacement. While Thomas Brown had no relatives in Australia, his wife had relatives who had earlier moved to Australia. One was John Maxwell of Liddleton Station at Glenroy, who had been superintendent of stock at Bathurst in 1828. Another was John Maxwell Irving who had taken up land at Glanmire (near Bathurst) in 1836.

On his arrival in the colony Thomas Brown applied unsuccessfully for a grant of land. He then crossed the Blue Mountains and using William Irving, as a sponsor, he leased Andrew Brown's property and Flourmill, "Cooerwull" at Bowenfels, for two years from 1 April 1839, as Andrew Brown was planning to return to Scotland to marry. During this time Thomas Brown and his wife, her brother and sister and nephew all lived in Andrew Brown's small cottage on the property. During the lease, part of Thomas Brown's duty was to oversee the construction of Cooerwull House for Andrew Brown. The lime for the mortar was obtained burning local limestone, and the coal needed for its production was dug from an outcrop in the hill near Farmers Creek just to the north of what is now the Lithgow City Sports Ground.

On 8 February 1840, the New South Wales Government Gazette advertised land for sale in Lithgow Valley. Thomas Brown brought 200acres (the first land sold in the valley) for £120/-. The next, and in following, years he brought more land. He built his permanent home in the Lithgow Valley probably in the year 1842. He named the house Esk Bank, after a river near his birthplace in Scotland. Indeed he tried, and failed, to rename the whole valley, Eskbank. It had already been named in 1827, on the recommendation of Hamilton Hume, after William Lithgow, Auditor-General of the Colony.

Earlier settlers in the district, such as James Walker of Wallerawang and Andrew Brown, of Cooerwull, were essentially farmers and graziers, Thomas Brown was an industrialist. He had come from a coal mining area in Scotland and the awareness of coal from his experience at Andrew Brown's property may well have assisted in his decision to take up land in the Lithgow Valley. The visit of the eminent geologist Rev. W. B. Clarke M.A., F.G.S. in February 1841, confirmed the presence of commercial quantities of coal in the valley, and it was after that visit that Thomas Brown made his second land purchase in the Lithgow Valley. At that time however, there was no market for coal locally, and no economic way of getting it to Sydney.

Nothing is known of Thomas Brown's activities from that time until 1852, when he was appointed a bench Magistrate at Hartley Court House together with James Walker, Andrew Brown and others. Later, in 1856, he was appointed Police Magistrate at a salary of £300/- a year. This seems to have been his sole source of income until the construction of rail to Bathurst via Lithgow. This happened in 1869 and the direction it would take was the subject of much research. From 1857, a young engineer, Edwin Barton carried out surveys between Windsor and Bathurst. Routes considered were through Mount Tomah, and the Grose Valley via a tunnel under Darling's Causeway. In the event, the way chosen was through Lithgow Valley, requiring construction of a Zig-Zag on the escarpment into the eastern end of the Valley, then northward through Wallerawang, and then west to Bathurst. In Lithgow Valley the line passed down the middle of the property of Thomas Brown, Barton's frequent host on his survey trips, and at Wallerawang through the property of James Walker, whose daughter Barton married.

Coal became a valuable commodity, not only because it could be carried cheaply to market, but also because the railways needed coal for the locomotives. Thomas Brown first opened a small mine, near what is now the site of the Sandford Avenue Bridge, but later shut this and opened the Eskbank Colliery, the site being near the present Lithgow Regional Library and the Lithgow City Council works depot in 1869 - Eskbank Colliery closed in 1903. Coal also made possible the establishment of heavy industry, on land leased from Thomas Brown such as: Eskbank Ironworks and the first iron ore Blast Furnace, Copper Smelting and an Abattoir for the production of frozen meat. Other coalmines soon followed after the railway was established in Lithgow. Lithgow's future as an industrial centre appeared assured and Thomas Brown became a wealthy man.

Thomas Brown resigned from the bench in 1871, and on 6 March 1872, he was elected as member for Hartley to the Legislative Assembly. Coal from his mine, Eskbank Colliery, had won the lucrative contract to supply the railways (1,000 tones a month) in 1872 and 1873, and again in 1876, even though the Eskbank price was, for this year, the highest of the four tendered prices. This led to a political storm, and as a result of the report from the Committee of Elections and Qualifications of the Legislative Assembly of New South Wales, dated 14 March 1876, Thomas Brown was disqualified from the Legislative Assembly. The contract was awarded to the Lithgow Valley Company for the rest of the year.

His wife, Mary died in 1878 and the next year he went for a visit to Scotland and on his return sold his Lithgow Estate to Rutherford of the Eskbank Ironworks Company for £45,000/-. In 1881 he built at his own expense, a Presbyterian Church which he named St Mary's in honour of his wife. It still stands, in Church Street, Lithgow however is no longer functioning as a church.

At the age of 74 years he left Lithgow to live at "Rockleigh", Edward Street, St Leonards, Sydney. He died there on 11 December 1889, and was buried in the Walker-Barton private cemetery at Wallerawang, where his wife, Mary, her sister Mina, her brother William, and her nephew James Maxwell had all earlier been buried. Thomas Brown and his wife had no children. His estate was valued for probate at £60.652/-. In his will he left instructions to sell all his estate. It was, after two small local legacies, divided equally among his ten brothers and sisters, none of who had come to Australia. All his personal papers were, as he had requested, destroyed after his death.