Rocky Flats (RF) is a former nuclear weapons manufacturing complex in Colorado, 26 km northwest of downwind Denver, at the eastern base of the Rocky Mountains ' Front Range. At RF, between 1952 and 1989, the Atomic Energy Commission (AEC) and its successors manufactured plutonium triggers. After remediation (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005), 4000 acres of buffer zone were transferred to the US Fish and Wildlife Service (USFWS), to manage as Rocky Flats National Wildlife Refuge (2007). Drawing on research materials from local libraries and archives, this essay explores the 'weapons to wildlife' (W2W) conversion of a militarized environment in Denver's 'Gunbelt'. The various phases in RF's demilitarization (closure, cleanup, transition to wildlife refuge and refuge management planning) are examined with reference to recognition of biodiversity value, debate over the ex-plant's future, and options for running a refuge still in an arrested state of development -closed to the public for want of funding. A further aim is to bring to the attention of physical geographers a growing body of scholarship by human geographers on environmental contamination at former nuclear sites and debates over remediation and post-industrial uses -and to contribute the additional perspective of an environmental historian.