Westfield Recreation Ground was one of 900 established by the Cargenie UK Trust, with the help of a grant of £200,000, the equivalent of £10m in today’s money, between 1927 and 1935.
The site is one of more than 100 sites identified by members of the public as part of the search launched by the trust and Fields in Trust last year, which was shared on social media as #FieldFinders.
Local historian and councillor Teresa Heritage identified the site as a Carnegie field and it has now been protected with a deed of dedication lodged at the Land Registry meaning it must remain as recreational land in perpetuity.
Town Mayor of Harpenden, councillor Nicola Linacre, unveiled a blue plaque on 16 February, marking the green space’s status. It the second Carnegie field to have a formal dedication. The first - Jubilee Park in Adlington Lancashire – signed off on the legal deeds earlier and was dedicated last July.
Fields in Trust has analysed the #FieldFinders submissions and shortlisted 20 sites which have already begun to make significant progress in improving legal protections associated with their site to protect them from future development. Other successful sites have also been discovered in Lossiemouth in Scotland, Lydbrook in Gloucestershire, and Stalham in Norfolk.
Douglas White, head of advocacy at Carnegie UK Trust, said: "A requirement of the original grant made by the Carnegie UK Trust more than 80 years ago to establish playing fields throughout the country was that these green spaces would remain public areas for the community in perpetuity. The aim of the new #FieldFinders campaign was to ensure that this legacy lived on.
"We were absolutely inundated with requests from members of the public upon launching the search last year and we are delighted with the result of being able to identify so many. Filtering through the entries and pairing them with the original 900 Carnegie fields sites is no mean feat and we thank the Fields in Trusts team for all of their efforts."
The sites shortlisted by Fields in Trust were also invited to apply for two improvement grants worth up to £5,000 as part of the campaign and the Westfield Recreation Ground was successful in winning one of these. Following local consultation the Carnegie improvement grant contributed to a major redesign project including a new Proludic playground and Trim Trail equipment and repositioning the multi-use games area.
Mayor Linacre said the town was "so pleased" to receive the funding and delighted with the improvements.
Fields in Trust chief executive Helen Griffiths said: "Our public green spaces are places to relax, play sports or hold community events. Ensuring they are around for years to come is a top priority so we are delighted that we have been able to protect these valuable assets for the long-term and to fund the improvements with Carnegie Trust Grants."
The Carnegie UK Trust is a charity founded by Andrew Carnegie in 1913. It was the last of the Trusts and Foundations he established. There are some 20 trusts, endowments and institutions endowed by Andrew Carnegie in the UK and Ireland, the USA and across the world.