National Natural Landmarks in 2023: Two New Sites, 74 Fiftieth Anniversaries

There are 604 National Natural Landmarks, and they sit on public and private land alike — a Marine Corps air station, state parks, university field stations, family forests. What they share is recognition as nationally significant natural places, and in 2023 two more joined them, 74 marked fifty years, and their stewards restored habitat, bought land and taught the public what makes each one special.

Two new landmarks

In December 2023, Secretary of the Interior Deb Haaland designated two new sites, bringing the total to 604:

• Glenwood Caverns and Iron Mountain Hot Springs, western Colorado — an excellent example of caves dissolved by both carbonic and sulfuric acid, a process that has run from the caverns' beginnings millions of years ago to the present. The hot springs hold active populations of diverse extremophiles living in thermal, sulfur-rich water; the caverns host unique ecosystems with cave-adapted species found nowhere else, unique biothems and fossilized extremophiles.
• John Boyd Thacher State Park, eastern New York.

Restoration that worked

• Miramar Mounds, inside Marine Corps Air Station Miramar in southern California, has mima mound–vernal pool terrain: small irregular hills of silt, sand and pebbles among small hollows that hold water part of the year. It includes 1,200 of the best of the air station's roughly 5,000 true vernal pools. Disturbed ground made room for more than 100,000 square feet of new pools, including dozens of basins built to offset the 1998 change from Naval Air Station to Marine Corps Air Station. Twenty-five years later they support thriving populations of three federally endangered species: San Diego mesa mint, San Diego button celery and San Diego fairy shrimp.
• Monarchs. The Pismo State Beach Monarch Butterfly Grove, part of the Nipomo Dunes and Point Sal Coastal Area landmark, is one of only five California sites that count more than 10,000 monarchs a year, clustering from late October to February in eucalyptus and Monterey cypress. At Point Lobos State Natural Reserve, park biologists are working with the Xerces Society for Invertebrate Conservation on western monarchs, whose numbers have fallen 95 percent since the 1980s through habitat loss and degradation, pesticides and climate change.
• Albany Pine Bush, New York, protects globally rare pitch pine–scrub oak barrens, home to the endangered Karner blue butterfly. In early 2023 the preserve commission and the Mohawk Hudson Land Conservancy bought more than 23 acres in the Town of Colonie, bringing the preserve past 3,400 acres and connecting it directly, for the first time, to a pine barren preserve in Schenectady.
• North and South Rivers, Massachusetts: a fall 2023 state grant funded a project to rank South Shore salt marshes by condition and ability to adapt to sea level rise, to guide restoration.
• Dragonfly mercury. For the seventh summer, landmarks sampled dragonfly larvae for the Dragonfly Mercury Project: in 2023, five sites in Pennsylvania, New Hampshire, Texas, Rhode Island and Maryland collected from 12 locations, adding to data from more than 160 other sites.

Recognition

Fifty years

Seventy-four sites were designated in 1973 — 36 by Secretary of the Interior Rogers C.B. Morton in late May, 38 more in early October — and celebrated their fiftieth anniversaries in 2023, among them McLean Game Refuge in Connecticut.

Grand Caverns park staff with the landmark's 50th-anniversary certificate at the Cave and Karst Expo. Credit: NPS.

The Lanphere and Ma-le'l Dunes, west of Arcata, California — California's 37th landmark, designated in January 2021 — was formally dedicated on May 18, 2023, the program's 61st anniversary, with an opening blessing by the Wiyot Tribe.

Unveiling the landmark plaque at Lanphere and Ma-le'l Dunes, California. Credit: Bureau of Land Management.

Teaching

• Fossils. After finds of a giant Jurassic sauropod's tibia and fibula in southern Colorado, a "Paleo To The People" symposium in Cañon City let the stewards of Garden Park Fossil Area and Indian Springs Trace Fossil Site explain their fossils. From fall 2023, each issue of Park Paleontology News features a paleontological landmark, starting with Ashfall Fossil Beds in Nebraska.
• Creelsboro Natural Bridge, Kentucky — "The Rock House," one of the largest natural bridges in the eastern United States and an example of stream piracy — was filmed for the Kentucky Life series, including how the landowner's parents fought in the 1980s to save it from a dam expansion that would have flooded it.
• Ice Age Floods. Grand Coulee is one of eight landmarks tied to the floods at the end of the last Ice Age, 18,000–15,000 years ago; hundreds joined Floodfest 2023 at Dry Falls, and all eight now appear in the NPS App under the Ice Age Floods National Geologic Trail.
• Sixth graders measured giant red cedars at Hobo Cedar Grove in Idaho, and two new coloring pages — a Devonian reef and a prehistoric ginkgo — brought the program's prehistoric life set to 15.

NNL sites detailed as part of the Ice Age Floods National Geological Trail within the NPS App.

Creelsboro Natural Bridge NNL plaque presentation to the Goff family. Pictured are NPS representatives with Thomas Henry Goff (holding the plaque), Mae Lorene Goff, and Diana Goff.

Sources

Based on "Landmark Highlights 2023" from the National Park Service's National Natural Landmarks Program, a work of the United States government in the public domain. Pictures an earlier version of this page left out were restored on 2026-09-26.