The founding Fox family was a Quaker dynasty whose business interests extended into shipping, foundry work, mining and gardens. They were related, in the unmistakable Cornish way, to nearly every other significant Falmouth family of the 19th century. Their Perran Foundry built marine engines, mining machinery and components for steam locomotives. They wanted a forum where their workers could present and discuss inventions: an audience for the practical creativity that the Industrial Revolution had unleashed. Robert Were Fox the younger, a Fellow of the Royal Society and an inventor of compasses for measuring magnetic dip at sea, was central to it. So was his brother Charles, a Quaker scientist who later developed Trebah Garden. Their sister Anna Maria Fox was equally active in promoting the Society, and her portrait still adorns the 1897 Annual Report. The Foxes turned an industrial circle into an institution.

In 1835 the Society built itself a permanent home: the Polytechnic Hall at 24 Church Street, Falmouth, designed by George Wightwick. It was specifically constructed for 'objects connected with the sciences, arts and literature,' but expressly not for theatrical performances; that restriction was only lifted in 1889 when the Society relented and permitted 'dramatic plays.' By 1837 there were local committees in Falmouth, Penryn, Truro, Redruth, Camborne, St Day, Helston, Penzance, Hayle, St Austell, Liskeard and Bodmin, plus a Ladies Committee. The total membership across these committees was 98. The Society had become a county-wide network for the transmission of scientific ideas, with the Falmouth hall as its centre.

The Poly's 19th-century role in Cornish mining was substantial. The Society was instrumental in developing the 'Man Engine,' a system that used the reciprocating motion of a pumping engine to carry miners up and down a shaft on linked platforms. Before man engines, miners climbed wet wooden ladders for hours to get to and from their working faces. The Society also worked on better drilling machinery, mine ventilation, and the welfare of miners and fishermen. In 1865 the Poly awarded its first silver medal for an explosive. The recipient was Alfred Nobel. The medal was for his new compound, nitroglycerine. The demonstration took place at Falmouth Docks: a small charge blew up a three-hundredweight wrought iron anvil; a larger charge scattered forty to fifty tons of rock. The Society also recognized Prentice's guncotton in the same period. Cornwall was where these new explosives got tested. The Poly was where they got their first medals.

The Society's scientific impetus faded somewhere in the late 19th century, paralleling the long decline of Cornish mining from the 1850s. The building stayed. Members ran exhibitions and lectures with shrinking ambition. From 1911 a license for 'Cinematograph Shows' brought films in, an arrangement that continued until 1931. During the First World War the Hall was variously a canteen, a dance hall, a concert venue and a hospital. The Second World War repeated the pattern, with the building used as a canteen and dance hall for HM Forces in 1942. By 1949 the structure was in a dangerous condition. The novelist Howard Spring, who lived in Falmouth from 1947 to 1965, joined the Society in 1947 and gave it a new lease of life, becoming president in 1953 and serving for eight years. A Falmouth Arts Centre was created in 1954 to give the Society a clearer public mission.

In January 2010 the trading company that ran the Poly's cinema programme went into administration. The Society was close to bankruptcy. What followed was the kind of community-led rescue that defines the institution's modern character: a 'Save Our Poly' campaign produced a totally new Board and a revitalised programme. In 2011 the Society formally adopted 'The Poly' as its working name, keeping 'Royal Cornwall Polytechnic Society' for legal purposes. In 2015 a new digital cinema system was installed. The Poly today shows independent films, hosts plays, comedy, talks and exhibitions, and owns the largest single collection of paintings and drawings by Henry Scott Tuke, the Falmouth-based painter of luminous seaside scenes. Over 200 works of his hang in or are owned by the Society.

There is a curious tail to this story. The polytechnic movement that began with the Falmouth Society spread across Britain over the next 150 years, with polytechnics established in Plymouth, London, Manchester, Glasgow and dozens of other cities. In 1992 all of them were converted into universities. Plymouth Polytechnic became the University of Plymouth. The London Polytechnic became the University of Westminster. The Royal Cornwall Polytechnic Society did not convert. It remained what it had always been: a learned society, an arts venue, a place where the people of Falmouth came to think about technique and culture together. As far as anyone can tell, this makes it not only the first polytechnic in the English-speaking world but, since 1992, the last one. The building on Church Street is older than nearly anything else in the polytechnic story. It is also still here.