Wheat was the dream that built this place. When McCrossin commissioned the mill, the Rocky River goldfields had swollen Uralla's population, and a flour mill seemed a sure thing in a hungry boomtown. Mitchell built to last: the ground floor walls are rough-dressed blocks of local white granite, infilled with smaller stones, with the front facade coursed in evener cuts and the upper two storeys rising in red brick laid in English bond. Inside, a sixteen-horsepower engine drove three sets of millstones, hauling wheat to the top floor and turning out roughly a thousand bushels of silk-dressed flour a week. Trapdoors and narrow chutes threaded grain and flour between the floors. It was the most ambitious building in the district. But wheat and flour never truly took hold on the cold New England tableland, and the gamble that raised the mill was, in the end, a losing one.

Buildings outlive their purposes. When milling faltered, the great granite structure slipped into long decades of more humble use. A chaff-cutting shed was added alongside in 1881, its first floor and steeply pitched roof carried on twenty-one round poles roughly 300 millimetres thick, power delivered from the mill through a wooden driveshaft punched through the western wall. From 1940 to 1979 the complex served as storage for McCrae's hardware shop and was known locally, without ceremony, as the "Wireshed." The shingled roof gave way to corrugated iron. A dovecote was pulled down. The building that had once been a statement of commercial confidence became a place to keep spare wire and odds and ends, its three storeys quietly waiting out the twentieth century.

Then a community decided the mill was worth saving. In 1979 the Uralla Historical Society bought the building, and over 1982 to 1984 its volunteers squared and stabilised the structure, demolishing rotted ground-floor flooring and scarfing or replacing decayed poles, with help from the Heritage Council of New South Wales. The museum opened on 2 May 1982, and its very first exhibition set the tone: "Thunderbolt, Life and Legend." In 1999 the mill was added to the New South Wales State Heritage Register, recognised partly for the simple oddity of so formidable a rural building standing in a village street. It remains owned and run by the historical society's volunteers, a museum, gallery and function centre rolled into one.

A failed flour mill turned out to be a perfect vessel for memory. McCrossin's Mill now holds the definitive collection of artefacts tied to Captain Thunderbolt, including a series of nine paintings by Phillip Pomroy depicting the events that led to Fred Ward's death near Uralla in May 1870. It also guards something unexpected: a nationally significant collection of Chinese artefacts recovered from the Rocky River goldfields, relics of the thousands of Chinese miners who worked the same diggings that once promised to keep the mill busy. The museum has built a reputation for exhibitions that are by turns empathetic, humorous and frankly strange. The building that wheat could not sustain is sustained instead by the stories Uralla refuses to forget.