The name Smithills derives from the Old English smeþe meaning smooth and hyll, a hill and was recorded as Smythell in 1322.

[4] Early medieval records about the hall began in 1335 when William Radcliffe acquired the manor from the Hultons who held it from the Knights Hospitaller.

In 1722 the Byroms of Manchester bought the manor and kept it until 1801 when the hall and estate were acquired by the Ainsworths, who made their fortune as the owners of bleachworks at Barrow Bridge.

[3] Around 1875 Richard Henry Ainsworth employed architect George Devey to extend and modernise the hall.

[3] A mass trespass of 12,000 people occurred in 1896 at Winter Hill on the route from Halliwell toward Rivington Moor in response to the hall's land owner Colonel Henry Ainsworth closing access to the moorland for his exclusive use for shooting, at what was then a vital route, Coal Pit Road, linking Bolton from Halliwell to Rivington and Horwich.

The road was used by many for access to the countryside, which had become a valuable resource as an escape from the industrially polluted towns and poor living and working conditions.

The oldest part of the structure is the great hall in the north range which was probably built in the early-14th century and was once surrounded by a moat.