NF- National Forest
NP- National Park
NM- National Monument
FWS- US Fish and Wildlife Service
NRA- National Recreation Area, often a designated subunit within a NF.
NWR- National Wildlife Refuge
NS- National Seashore
And for Wanderers back East---
BRP- Blue Ridge Parkway
VCT- Virginia Creeper Trail
GSMNP- Great Smoky Mountains NP
SNP- Shenandoah NP
AT- Appalachian Trail (pronounced appa-LATCH-chun)
OBX- Outer Banks
IBX- Inner Banks
CHNS- Cape Hatteras NS
CLNS- Cape Lookout NS
ANS- Assateague NS
ES- Eastern Shore (lower portion of the Delmarva Peninsula, location of the ANS).
COE- US Army Corps of Engineers (operators of many hydroelectric and flood control dams and canal systems)