St Helena Mill is of interest as one of Bolton's oldest mills and contrasts in size, materials and scale of its power system with the larger early mills in Manchester. The eleven-bay steam-powered mill was built in the late 1820s with four storeys and an attic. It stands partly on the site of an earlier water-powered cotton mill, built circa 1780. It may have originally been used for fine cotton spinning, but from the late 1830s was occupied by Robert Walker and for cotton waste spinning, probably on mules. Its continued use as a cotton-waste mill probably explains the survival of the building; it is of similar dimensions to purpose-built cotton-waste mills of later date. The site also includes a small attached north-light shed and two red brick extensions of 1897 and 1906.
The walls are of rubble stone with small flat-headed windows. There are rows of taking-in doors to the south end and the east side. The north end wall is of brick and may be a later rebuilding. The joisted timber floors are supported by a single row of columns to which line shafts were attached. Other line shafts were supported from the beams. The gabled attic has queen-strut trusses and was also used for powered processes.
The mill continued to be used for cotton waste spinning until 1979 and by 1999 the two extension had been demolished and the mill refurbished. Now the the probation office for the Bolton District.