St Austell takes its name from Austol, a 6th-century Cornish saint associated with the Breton missionary tradition. A 10th-century Vatican manuscript lists him among the Cornish saints whose parishes were already recognized around 900 AD, which suggests St Austell existed as a religious community long before it was a town. The current parish church dates from the 13th and 14th centuries with a major extension in 1498-99, the join between the two phases still visible in the stonework. All four outside walls bear carved sculptural groups: the Twelve Apostles in three groups around the building, the Holy Trinity above the Annunciation on the west wall, and the Risen Christ between two saints below. The tower dates between 1478 and 1487 by the arms of Bishop Courtenay, faced in Pentewan stone with the texture of dressed cream. Inside, the granite-lined walls feel monastic. Outside, a Cornish cross found buried in a Treverbyn field in 1879 stands on a new base in the churchyard.

China clay is kaolinized granite, the feldspar in ordinary Cornish granite broken down by geothermal action into a fine white aluminium silicate. The Chinese had mined and refined it for porcelain for over a thousand years. European potters spent the 17th and 18th centuries trying to figure out how. William Cookworthy first identified usable deposits at Tregonning Hill in west Cornwall in the 1740s, then found vastly larger quantities in the Hensbarrow Downs north of St Austell. He patented hard-paste porcelain manufacture in 1768, transferring his patent to Richard Champion of Bristol five years later. The pottery trade did not stay in Cornwall, but the raw material did. By the mid-19th century, china clay had eclipsed tin and copper as the principal industry around St Austell. When metal prices crashed, miners switched to clay. The white pyramidal tips of waste sand still rise across the landscape north of town, what locals call the Cornish Alps, marking where decades of pit work has turned hills inside out.

Tin built the town and clay made it rich, but Methodism shaped how it lived. By 1839 the West Briton newspaper recorded 37 non-conformist chapels in St Austell, in a town of perhaps 4,000 souls. Wesley himself preached here. The chapels poured the rituals of Cornish working life into their own moulds, and many still stand even where the congregations have dwindled. The St Austell Brewery was founded in 1851 and celebrated its 150th anniversary in 2001, growing into one of the largest independent regional brewers in the country. Its flagship beer Tribute is sold across Cornwall and beyond. The Seven Stars Inn on East Hill, the brewery's first pub, was purchased in 1863 and still stands, though now let by the brewery to an educational charity for young people. The brewery museum and visitor centre on Trevarthian Road still pulls in tourists who want to see where the malt actually goes.

St Austell rebuilt itself in concrete in the 1960s, a brutalist precinct of reinforced shops and offices that aged badly through the 1980s and 1990s. In the 2000s a 75 million pound redevelopment dismantled most of it and replaced it with White River Place, named after the kaolin-stained streams that drain the clay country. The Filmcentre, originally a 1936 Odeon, was demolished in 2007. A new purpose-built cinema, the first in Cornwall for over 60 years, opened in December 2008. The bigger reinvention happened just north of town. In an exhausted china clay pit at Bodelva, Tim Smit's Eden Project opened in 2001: a pair of geodesic biomes the size of small stadiums, planted with the world's flora and engineered to demonstrate what ecological literacy looks like on a Saturday afternoon. China clay scarred the landscape; the Eden Project showed what the scar could become. The China Clay Country Park at Wheal Martyn, two miles north of the town, tells the parallel story: the men, women and children who lived, worked and played in the shadow of the clay tips, in a single industry that defined the place.