Mason Neck National Wildlife Refuge was specifically created to protect essential bald eagle nesting, feeding, and roosting habitats along the Potomac River. Along with active eagle nesting, the refuge hosts a rookery containing more than 1,200 nests for great blue herons.

The 2,276-acre refuge, adjacent to Mason Neck State Park, contains about 2,000 acres of hardwood forest, the largest freshwater marsh (285 acres) in Northern Virginia, and nearly six miles of shoreline.

Visitors can view the refuge along two trails, one through woods and one in Great Marsh. In the spring, wildflowers fill the woods as songbirds migrate through the area and various types of ducks feed along the creeks and marsh. In the summer and fall, birds such as egrets and herons dominate the marshes before many of them travel south for the winter. From November to February, bald eagles breed and lay eggs.