After years of negotiation, Allerdale council and Cumbria County Council have officially purchased the former armaments depot from the Ministry of Defence.
The 1,050-acre site between Cockermouth and Maryport is one of the largest brownfield sites in the UK. It will now be marketed to developers to generate ideas for leisure and commercial uses.
Cllr Joe Milburn, leader of Allerdale council, said: "The development of Derwent Forest has been a long-held vision for Allerdale Borough Council and I am delighted that this important milestone has been reached. Derwent Forest has immense potential to raise the profile of west Cumbria at regional and national level, attract inward investment to the area and create jobs and training opportunities, which will impact positively on local communities."
Other partners in Derwent Forest are the North West Development Agency, economic development agency Cumbria Vision and West Lakes Renaissance, the urban regeneration company for Furness and West Cumbria.
The NWDA will fund site maintenance, security costs and marketing of the site for three years. If after that time a developer has not been found, the two councils will either retain ownership of the site or sell it on the open market.