The Park has been created on the former grounds of two mental hospitals.

The northern area of the Park is where Hill End Hospital was located. It was opened in 1900. It even had its own railway line and during the 2nd World War was used by St Bartholomew’s to treat the war wounded and Londoner’s injured during the Blitz. The Hospital was a self-sufficient community in many respects and during the 1960's pioneered work in Community Care. Only three of the original Hospital ward blocks now remain and these have been converted into social housing. The former Hospital Chapel has been redeveloped with the aid of Arts Lottery funding and is now the base for the Trestle Theatre Company and Trestle Arts Base.

Cell Barnes Hospital

The south of the Park is where the Cell Barnes Hospital was located, opening in 1933 and closing in 1998. Very little of the former Hospital remains only West Lodge, the Birch Centre, and the former Nurses Home.

Creating Highfield Park

Following the Hospital closures, the planning authorities of St Albans City and District Council approved the redevelopment of the Hospital sites with nearly 700 new housing units on the condition that 60 acres be set aside as public open space. Instead of following the traditional way of developing a Park, St Albans City & District Council established the Highfield Park Trust as an Independent Charity and as part of the development process secured funding from the Secretary of State for Health and provided it with an endowment to enable it to develop and maintain the Park.

Trustees and staff were recruited and the Trust has worked closely with many agencies and housing developers to secure, protect and establish the Park. This way of managing open space is unusual but it does "empower" the local community to influence their local environment. The Trust has a lease of 150 years from St Albans City & District Council