The Mary Dendy Hospital was opened in 1908 as the Sandlebridge Boarding School (often referred to as the Sandlebridge Colony) by the Incorporated Lancashire and Cheshire Society for the Permanent Care of the Feeble Minded; this Society was founded in 1898, by members of the Manchester School Board, who had noted the inadequacies of educational provisions made for mentally deficient (feeble minded) children of school age.
The Society moved children to Sandlebridge in 1902 and opened the schools in 1908, as the first permanent residential care for mentally deficient children in Britain.
In 1933 on the death of Mary Dendy (a leading member of the Manchester Schools Board and later President of the Society) the schools were renamed the Mary Dendy Homes in recognition of her pioneering work for mentally deficient children.
The homes continued to be run by the Society until 1941, when they were transferred to Cheshire County Council (discussions having started in 1939). The Society went into voluntary liquidation in May 1942.
The homes were renamed the Mary Dendy Hospital in 1948, when they became part of the National Health Service. The hospital was managed by Cranage Hall Hospital Management Committee until 1974, when it became part of Crewe Health District within Cheshire Area Health Authority. In 1982 it was transferred to Macclesfield District Health Authority. In 1983 it had beds for 375 mentally handicapped patients.