After 1700 millwrights built and maintained wind and water mills in increasing numbers. At the time they were the largest machines ever constructed.

Millwrights possessed many skills. William Fairbairn noted that

'the ordinary millwright was... a fair arithmetician, knew... of geometry, levelling and mensuration, and... possessed a very competent knowledge of practical mathematics. He could calculate the velocities, strength, and power of machines: he could draw in plan and section.'

They were the best-qualified men to build James Watt's steam engines.