No one is quite sure who Saint Just was. Some say Justus, the seventh-century Archbishop of Canterbury - but Cornwall's long resistance to the edicts of Canterbury and Rome makes this unlikely. A better candidate is Saint Iestyn, a sixth- or seventh-century Cornish saint said to be the son of Geraint ab Erbin, a ruler of Dumnonia. In 1478 the English topographer William of Worcester recorded a local tradition that the church contained the bones of Justus of Trieste. Whoever the saint was, the parish that took his name became one of the most ancient settlements on the Penwith peninsula. Around the modern town are antiquities older than any saint: Ballowall Barrow, a chambered Neolithic tomb on the cliff toward Cape Cornwall, and the standing stones, hut circles, and field systems that thread the moors above the coast.

The Church of St Just in Penwith is a fine 15th-century granite building rooted in something older. In 1336 the church here was rebuilt and rededicated by John Grandisson, Bishop of Exeter; only the chancel of that medieval church survives, while the nave and aisles were rebuilt in the 15th century. The Feast of St Just commemorates that 1336 dedication. It used to fall on 13 July; in 1536 an Act of Henry VIII moved it to the Sunday nearest All Saints' Day, so the modern Feast usually runs from the last weekend of October into early November. Feast Sunday is a church service and civic procession; Feast Monday is the popular celebration. "Rich and poor still at this season keep open house," wrote one observer in 1882, "and all the young people from St Just who are in service for many miles around, if they can possibly be spared, go home on the Saturday and stay until the Tuesday morning."

The 19th century made St Just one of the most important mining districts in Cornwall. Within a few miles of the town stood the engine houses and dressing floors of Boscaswell Downs, Balleswidden, Parknoweth, Boscean, Wheal Owles, Wheal Boys, Levant, Botallack, and Geevor - some of the most productive tin and copper mines in the world for a few decades. The Great Western Railway had once planned to make St Just the terminus of the London-to-Cornwall mainline; when those plans were abandoned, the town was left without a railway and with mines that were exhausting themselves anyway. Tin prices collapsed. The 1861 population of nearly nine and a half thousand was halved by 1900 and halved again over the century that followed. In 2006 the whole landscape - mines, engine houses, harbours, miners' cottages, smelting works - was inscribed as the Cornwall and West Devon Mining Landscape UNESCO World Heritage Site. The 2021 census put the parish at 4,695.

At the heart of the town is the Plain-an-Gwarry, locally pronounced Plain an Gwarry: a medieval Cornish playing place, one of only two surviving nearly complete in Cornwall. It is a low grass-banked circle in the middle of the streets, used historically for Cornish wrestling tournaments, open-air theatre, and instruction. Productions of the Cornish Ordinalia mystery plays still happen here from time to time, in modern revivalist Cornish. James Warren (born 1786) - known as Little Jem Warren, Little Hercules, or Great Jem - was a St Just wrestling champion who fought all over Britain and helped rescue survivors when the East Indiaman Kent caught fire. Thomas White of St Just trained Jack Carkeek, who went on to win the American Cornish wrestling championship multiple times and claim world championship titles in the United States. The Star Inn, on Fore Street, has been called the last proper pub in Cornwall; its clientele on any given evening includes farmers, retired miners, birdwatchers, and the occasional Cornish-language enthusiast. Every July the town gives itself over to Lafrowda, a seven-day community arts festival that fills the Plain with music, costume, and the smell of pasties.

Two place names tell you where St Just's emigrants went. There is still a district of Bendigo, in the Australian gold country of Victoria, called St Just Point - settled by St Just miners who took ship in the 1850s and 1860s for the Australian gold rush. There is also a sister relationship with Nevada City in California, where another wave of Cornish miners pushed for the silver and gold of the Sierra Nevada foothills. Both towns remain twinned with St Just, in partnership with Penzance. The artistic community survives in the present: the painter Kurt Jackson lives and works nearby; the folk singer Martha Tilston wrote The Cape on her 2010 album Lucy and the Wolves, inspired by Cape Cornwall. St Just is twinned with Bendigo, with Nevada City, and with the gentler ghost of a town that 9,290 people once filled before the tin gave out. It is still the most westerly town in mainland Britain. The Atlantic is close enough to taste.