North-western residential suburb, named for Constable John Thorn, who was granted the land after the capture of a dangerous gang of bushrangers in 1830. 'Leigh' is the old English name for a meadow or cleared forest land.
Named for John Thorn, to whom the land was granted as a reward for capturing bushrangers, Thornleigh became an orchard and dairy district, with a quarry that provided rock for the railway line that went through in the 1880s. Citrus fruit and vegetables grown in Thornleigh went to the Sydney markets by rail.