There has been a Christian site here since the sixth century, when the place is said to have been founded by St Elaeth — a saint about whom early Welsh tradition is generous and modern history is cautious. The medieval church that preceded the present building was small, low, and increasingly inadequate as Amlwch grew. Planning for its replacement began in 1787. The Copper Mines Company put up most of the construction money; Thomas Williams gave six hundred pounds (a substantial sum then — equivalent to many tens of thousands of pounds today); Henry Paget, 1st Earl of Uxbridge, who owned a share of the mining works, also contributed, as did the Reverend Edward Hughes, another mine investor. Estimates of the total construction cost differ. Writing in 1833, the Welsh antiquarian Angharad Llwyd put it at £4,000; the topographer Samuel Lewis, writing sixteen years later, said £2,500. Either way, it was a church built with the wealth of an industry that had transformed the surrounding landscape into something resembling a moonscape — Parys Mountain remains one of the most striking industrial ruins in Britain.

Most Anglesey churches are small, low, medieval, and built of rubble masonry. St Eleth's is none of those things. It is a tall, dignified, Neo-classical building set back from the east side of Queen Street, with an impressive tower and an interior that retains, in the words of a 2009 architectural guide, 'considerable grace', with columned arcades 'touched by a breath of classicism'. The 1951 listing description called it 'a substantially Neo-classical church retaining much of its original architectural character'. It is Grade II* listed — the second-highest level of statutory protection in Wales, reserved for buildings of more than special interest — and the lychgate at the church entrance has its own Grade II listing as a good early example of a characteristic local nineteenth-century type.

Thomas Williams of Llanidan deserves a paragraph of his own. A solicitor by training, born on Anglesey in 1737, he ended up controlling effectively the entire British copper industry for a generation. He sat in Parliament. He banked. He sheathed the bottoms of Royal Navy warships in Anglesey copper. He used the wealth from Parys Mountain to buy mines elsewhere, including the Cornish workings whose owners had been his fiercest rivals. By the time he died in 1802 he had made a personal fortune that was, in proportion to the economy of the age, enormous. A small portion of it built the church in Amlwch, which sat — when it was new — at the centre of a town that he had effectively conjured into being. A 2006 guide to the churches of Anglesey describes St Eleth's now as 'a good example of a tastefully restored church', and 'a spacious, high sided building with an impressive tower'. The Copper King paid for the bones of it. Subsequent generations have looked after them.

Amlwch at the height of the copper boom had a population of perhaps six thousand — more than Bangor or Caernarfon — and a port at Porth Amlwch dug out by hand from the rock to handle the ore ships. The mountain itself was stripped of vegetation, riddled with adits, and dyed yellow, red, and orange by the iron-rich minerals exposed in the workings. When the easy ore ran out in the early nineteenth century the town began a long contraction, and by the time the mines closed for good in the early twentieth century, only a few hundred people were still mining. What remained was the architecture of the boom: the docks at Porth Amlwch, the workers' terraces climbing the hills, the unusual harbour-side parish church of St Eleth's Holyhead Road sister Our Lady Star of the Sea, and at the centre of it all, the bright tower of St Eleth's, still ringing for services within the Church in Wales — one of four churches in the modern parish of Amlwch, still doing what it was built to do.

St Eleth's sits at 53.410°N, 4.345°W, in the centre of Amlwch on the north coast of Anglesey. From the air, the church tower is a clear vertical landmark in a town that is otherwise low and tucked into the hillside. The visible relationship with Parys Mountain (3 km south-southwest, recognisable by its multi-coloured spoil-heap landscape) explains the church's existence — they are siblings of the same eighteenth-century industrial boom. Porth Amlwch, the engineered harbour that exported the copper, is half a kilometre to the north. RAF Valley (ICAO EGOV) lies 22 km to the southwest. The Skerries lighthouse and the open Irish Sea fill the northern horizon.