At Fahnestock State Park, the institute orchestrated 13 land transactions, representing 8,040 acres, bringing the total acreage there to 14,337. At Sterling Forest, the institute worked with the Trust for Public Land and the nonprofit environmental group Scenic Hudson to buy three parcels with a combined acreage of 14,570, which forms the bulk of the park’s 19,131 acres. And the institute doubled the size of the 2,165-acre John Boyd Thacher State Park outside Albany, through eight acquisitions totaling 1,202 acres.

At Minnewaska, the institute long ago formed a partnership with the Nature Conservancy’s eastern New York chapter. The Nature Conservancy helped establish the park, buying its first 7,100 acres in 1970 and selling the land to the state. The property had belonged to a local family, but was in foreclosure.

“There was certainly the threat of development, and the conservancy recognized that it was a special property in terms of the ecology and the beauty,” said Cara Lee, director of the Nature Conservancy’s Shawangunk Ridge program.

The largest single acquisition at Minnewaska by the Open Space Institute came in 1997, when the group bought 4,780 acres in Sam’s Point Preserve, on the border of Ulster and Sullivan Counties. In 2006, the state acquired most of that land, adding it to the park. But the final 1,063 acres, which the state will soon buy, continued to be held by the institute and managed by the Nature Conservancy, which built a visitors center there in 2005.