Jonathan was born in Staffordshire on 30 October 1717, the eldest of the four children of steam pioneer Joseph and Rebecca (née Haywood) Hornblower.
Joseph Hornblower was an installer of Newcomen steam engines in the Cornish mines and taught his children the same trade.
Jonathan eventually took over from his father around 1740 and moved to live and work in Cornwall, where he built and installed Newcomen engines at several mines.
He married Ann Carter of Broseley, Shropshire, a lawyer's daughter, on 16 July 1743 and fathered thirteen children, all given biblical names beginning with J.
This article about an engineer, inventor or industrial designer from England is a stub.