Map from “The round of applause heard ’round the county” by Ken Hemphill at Neighbors for Crebilly, 9/18/18. Green = municipalities that have passed open space referenda or other measures to buy or preserve open space, 1992-. Blue = not. Yellow = urban areas. Click on the list of municipalities there for details.
See also the detailed “parcel map” of preserved open space on the Chesco web site. Or dwnload (through 2016) here: ProtectedOpenSpace2016_201708011325275412. The good news is that all municipalities in the county, even those with no formal municipal actions, have protected open space, in some cases quite substantial.