Toowoomba grew up on Giabal country, on the tableland the Giabal had shared for at least 40,000 years with the Jarowair to the north and the Jagera along the escarpment, peoples dispossessed within a single brutal decade as pastoral stations swallowed the Downs in the 1840s. By the 1860s the colonial town needed the machinery of colonial law. The two-storey brick courthouse opened in 1863, and a gaol rose on government land directly behind it to hold those arrested across the Darling Downs, the Maranoa, and the Warrego while they awaited trial. By September 1864 the prison's boundary wall was complete: a wall two bricks deep on dressed-stone footings, about twelve feet high, with tapered buttresses. That wall, against all odds, is largely what remains.

The building's hardest chapter began in 1882. By then the men were gone, sent to St Helena Island, and the Toowoomba gaol had been turned over to women prisoners from across Queensland. There was no provision for the youngest among them, so the old courthouse was converted into a female reformatory. The records are plain and difficult: girls were lodged here, some as young as four or five. They slept in compartments around a dining room, were schooled in a room that seated 22, and were put to work in a well-appointed laundry, washing for local families under the era's iron conviction that such children must labour. Two cells called darkrooms, for serious offenders, lay beneath the rear of the building. These were not criminals in any sense a modern reader would recognise. They were poor and orphaned and abandoned children, swept into an institution because the colony had nowhere else to put them. The reformatory closed in 1903, and the children were moved to Brisbane.

When the gaol was abandoned, Toowoomba's cultural ambitions moved in. The poet George Essex Evans had returned from a Maryborough eisteddfod fired with the idea of making Toowoomba a centre of music, art, and literature, and the inaugural Austral Festival in 1904 was a triumph. To house future festivals, supporters bought the old gaol site and hired architect William Hodgen, who did something inspired and thrifty: he used the massive stone-rubble prison wall itself as two walls of a vast new hall, so the building cost a fraction of what it should have. The former reformatory became the Austral Museum, its first exhibits including South Sea Islander artefacts and samples of every soil in Queensland. The festivals faded after Evans died during the 1909 event, but the hall and museum had given the grim site a wholly new life.

After the museum came a private hospital, then a boarding house, then a guesthouse called Rutlands run by the Thompson sisters from about 1930 to 1960. When they sold the 19-room house, the buyer was the Toowoomba chapter of the DeMolay Order, a youth organisation, and the building has carried the name DeMolay House ever since, the only branch in the world to own its own premises. Restorers have turned up the building's buried past in passing: old roof shingles, cast-iron pipes, and, beneath the floorboards, a child's shoes and a little girl's dress. Outside, the prison wall endures. A corner of it still rises from Stirling Street, and a modern block of townhouses uses the old gaol wall as part of its foundations, the nineteenth-century stone quietly holding up the twenty-first century above it.