Watch a report by ITV News Anglia's Russell Hookey
29 sites in the East have been added to Historic England's at 'Risk Register' because of concerns about their condition.
Among them, The Grade I listed Plume Library in Maldon, which is one of the oldest public libraries in England.
The late 17th century library was built on the site of the former church of St Peter and has over 7,000 volumes, mostly from the 16th and 17th centuries.
The lath and plaster ceiling over the library is at risk of collapse, with cracking in various parts of the building.
Maldon Town Council and The Plume Library Trust have raised around £80,000 towards urgent repairs.
A Grade II listed fort in Harwich is also at risk of being lost.
The Redoubt was built in the 1800s, as part of the Martello Tower chain of defences against a possible invasion, stretching from Aldeburgh to Seaford.
A 180ft diameter circular fort with ten guns on the battlements, the Redoubt defended the port of Harwich.
But it is now suffering the effect of leaks and damage to the inner and outer moat walls and there is significant plant growth internally.
It is the varied tapestry of our historic places that helps us define who we are. In testing times such as these, heritage gives us a sense of belonging, continuity and comfort. We also know that investing in historic places can help boost our economic recovery.
Other historic sites most at risk of being lost forever as a result of neglect, decay or inappropriate development include:
Parish Church of St Leonard, Old Warden, Bedfordshire
Church of St Andrew, Northborough, Peterborough, Cambridgeshire
Buckden Towers, Buckden, St Neots, Cambridgeshire
Stone Hall, Little Canfield, Saffron Walden, Essex
St Peter’s Church, Great Yarmouth, Norfolk
Church of All Saints, Walsoken, Norfolk
Church of St Andrew, Mutford, Suffolk
Over the last year, 24 historic buildings and sites in the region have been saved and removed from the register, thanks to the work of local communities and charities.
Church of All Saints, High Street, Houghton Regis, Bedfordshire
Guildhall, Thaxted, Essex
Town House (Ashwell Museum), Baldock, Hertfordshire
Wheathampstead earthwork incorporating Devil’s Dyke and the Slad, Wheathampstead / Sandridge, Hertfordshire
Historic England has offered £1.77m in grants to help bring some of the region’s most important historic sites back to life.