With his two brothers, Jeremiah and Thomas, he took over the lease of Anthony Bacon's cannon foundry at Cyfarthfa, before they began the Penydarren Ironworks during the 1780s. In 1784, after a court case they transferred the lease of the foundry from Anthony Bacon (with whom they had quarrelled), who reassigned it to David Tanner, and moved to where they had set up the works on the banks of the River Morlais, building Penydarren House on the far side river bank. After years of fierce competition with the Dowlais and Cyfarthfa ironworks, they began to prosper. Samuel took over as proprietor of the Penydarren works, while Jeremiah moved to Ebbw Vale.
Samuel was one of the chief promoters of the Glamorgan canal, which opened in 1795 and cost £103,000, of which he subscribed £40,000 and which enabled the transporting of heavy manufactured iron to Cardiff docks. In 1804 Samuel won a 1000 guineas wager with Richard Crawshay as to which of them could first build a steam locomotive for use in their works. Homfray employed Richard Trevithick for this purpose and his locomotive won the bet, hauling five wagons, carrying ten tons of iron and seventy men, at a speed of five miles an hour.
In 1800, Samuel married Jane Morgan, daughter of Sir Charles Gould Morgan, 1st Baronet of Tredegar House, and thus obtained a favorable lease of mineral land at Tredegar, where he established the Tredegar Ironworks. In 1813 he was appointed High Sheriff of Monmouthshire and in 1818, returned as Member of Parliament for Stafford borough.
Of the children of Samuel and Jane Homfray:
- Two sons. Watkin Homfray (1796–1837) and Samuel Homfray the younger (1795–1883), went into the iron business
- Amelia married joint owner of the ironworks William Thompson (1793–1854)
- Mary, the youngest daughter, married George Darby, Member of Parliament for East Sussex, and had a family of four sons and eight daughters
- Merthyr Historian, Vol 15, pp.33–35
- "Welsh Biography Online". National Library of Wales. Retrieved 17 February 2011.
- Ince, Laurence. "Homfray family". Oxford Dictionary of National Biography (online ed.). Oxford University Press. doi:10.1093/ref:odnb/47499. (Subscription or UK public library membership required.)
- Burke, Sir Bernard (1871). A Genealogical and Heraldic History of the Landed Gentry of Great Britain & Ireland. Harrison. p. 321. Retrieved 20 December 2017.
|Parliament of the United Kingdom|
| Member of Parliament for Stafford
With: Benjamin Benyon
Sir George Chetwynd