Kayakers enjoy a fall day on Nanjemoy Creek.
Nanjemoy Creek Kayakers enjoy a fall day on Nanjemoy Creek. © Alan Eckert Photography

Places We Protect

Nanjemoy Creek

Maryland / DC

One of Maryland's most pristine watersheds.


Check out an aerial photo of Nanjemoy Creek in Charles County and you’ll see why it has been called “the green thumb” of the Potomac River — about 80 percent of the land in the Nanjemoy watershed remains forested.

Relatively few roads carve through these woods, though human activities like residential development and incompatible forestry threaten this emerald-green oasis. The Nature Conservancy has embraced the challenge: retain the character of one of the state’s most pristine watersheds, where just eight percent of the land is currently protected.

The Conservancy has identified a project area of more than 48,000 acres offering the rare opportunity to save and restore this enormous block of contiguous forest. This remarkable situation exists, in part, because the landscape has not been fragmented as it has in other places — only about 150 private landowners own 25,106 acres (76 percent) of the unprotected land here.

Since establishing Nanjemoy Creek Preserve in 1978, The Nature Conservancy has worked to assemble the forest puzzle, helping conserve more than 3,510 acres to date (3,204 of which is the Conservancy's preserve).

What You'll See

The preserve was established to protect a large breeding colony of great blue herons that once nested here.  The herons have since moved on, but the preserve abounds with life. 

Local farmer and naturalist Calvert R. Posey, site manager for many years, kept a detailed field journal listing 48 tree species, 86 wildflowers (including rare Virginia wild ginger), and numerous creatures — snakes, skinks and salamanders, to name a few. Posey noted that his lists on this richly endowed place were by no means complete.

The Conservancy’s ultimate goal is to protect a forested ecosystem large enough to function as nature intended it, and also large enough to encompass most, if not all, common and rare species. Raccoons, bobcats, skunks, and squirrels inhabit the woods; otters swim the creek; and the rare dwarf wedge mussel (found in only 20 sites worldwide) thrives in the sandy-mud bottom of stream banks. The deep forests here also attract many species of migratory songbirds.

Current Conservation at Work
  • Recent land acquisitions include a tract that was a missing slice from the core of the Conservancy’s conservation “pie,” adjacent to Conservancy land as well as protected state and federal land.  Sixteen interior-forest bird species find haven here, including five that are particularly sensitive to their surroundings. Wetlands provide breeding habitat for reptiles and amphibians.  This property is upstream from one of the two most viable populations of the dwarf wedge mussel in Maryland; protecting this section of forest will help maintain water quality for this vulnerable species. 

  • Another recent land acquisition of 275 acres is contiguous with 1,282 acres of protected state and federal lands, as well as 2,300 acres of Conservancy lands.
  • To protect our native forests, we have been controlling invasive Ailanthus trees that have been spreading throughout the preserve.

For more information about Nanjemoy, contact Gabe Cahalan at (301) 897-8570 or gcahalan@tnc.org.