An official website of the United States government
Here's how you know
Official websites use .gov A
.gov website belongs to an official government
organization in the United States.
Secure .gov websites use HTTPS A
lock (
) or https:// means you've safely connected to
the .gov website. Share sensitive information only on official,
secure websites.
The NNL program was established in 1962 with the first site designations occuring in 1964. Since that time, individual NNL sites have reached their Golden Anniversary, or 50 years, of landmark designation. The milestone is remarkable in that it recognizes 50 years of voluntary conservation, committment, and partnership with landowners and managers of these NNL sites.
In 2025 we recognize and celebrate the Golden Anniversary of 29 NNL sites. These NNLs were officially designated when then Secretary of the Interior, Stanley K. Hathaway, signed the designation memos on May 15, 1975.
Mona and Monito Islands NNL, located in Puerto Rico, was designated on May 15, 1975. Pictured is a photograph from the original evaluation of a cave entrance at Cueva del Diamente, near Sardinera Beach on Mona Island.
NPS photo
Sites Designated May 15, 1975
Deep Springs Marsh, California
Fish Slough, California
Mitchell Caverns and Winding Stair Cave, California
Russell Lakes, California
Hagerman Fauna Sites, Idaho
Anderson Goose Lake, Iowa
Dewey's Pasture and Smith's Slough, Iowa
Rock Creek Research Natural Area, Kentucky
Bigelow Mountain, Maine
New Gloucester Black Gum Stand, Maine
Cedar Creek Natural History Area-Allison Savanna, Minnesota
