Rayleigh Windmill is a grade II-listed mill which was built in 1809 for local timber trader Thomas Higgs. He became bankrupt in 1815 and the mill was sold on to numerous individuals. It was the last of five mills which served the town throughout history. The mill had to be repaired in or just after 1869. Thomas James Brown was the last miller to use the mill via wind around 1907, and hence the cap and sails were removed two years later. It was instead worked via steam engine, then oil, and finally electrically until at least 1937. In 1970 the windmill was reopened for use as a museum by Rayleigh and District Antiquarian and Natural History Society. The mill had no wooden weather-boarded cap as seen today, and stood with added crenellations to look like a castle tower until 1974 when they were remade. A great deal of restoration took place in 2005, and it has recently closed (as of late 2017) for works. Check here for opening times. It is open as a museum now, and one of the millstones can be seen in the garden area around it.
Sources: Windmill World, Wikipedia