English Heritage has been given £80m in the government's Spending Review as part of plans for the organisation to become a charity by 2015.
The new charity will manage the National Heritage Collection, which includes Stonehenge and Dover Castle.
The government currently contributes £22m annually towards the collection. The aim is for the charity to eventually become self sufficient.
Other powers such as listing buildings will remain government funded.
The new official body, which will also advise on planning, has a working name of the National Heritage Protection Service.
'Bring England alive'
The new charity will still be called English Heritage and the 420 sites in the National Heritage Collection - which include London's Kenwood House, and Charles Darwin's home in Kent - will remain in public ownership.
Government funding for the charity will be tapered down from 2015 eventually to nothing, meaning it will have more freedom than now to generate income from commercial activities and philanthropic donations.
Some of the £80m awarded by the government will help to set up the charity so it will be fully operational by March 2015.
In a statement, the government agency described the planned changes, which will be subject to a consultation, as "an excellent outcome".
"This year we have been celebrating 100 years of state protection for heritage and today's announcement sets the scene for the next century.
"The government's £80m investment and the creation of the new charity will help us preserve the National Heritage Collection for the future, be true to the story of the places we look after, to aim for the highest standards in everything we do from our conservation work to the way we run our events and to provide an experience that brings the story of England alive."
The announcement came as the government said there would be cuts of up to 5% in funding for museums and the arts in the Spending Review for 2015-2016.