If the millions of drivers crossing the Garden State Parkway bridge between Atlantic and Cape May counties look west, they’ll see the big end of one of New Jersey’s more unusual national parks.

That broad river flowing into the bay is the Great Egg Harbor River, a National Scenic & Recreational River established by Congress in 1992 and made a unit of the National Park Service. Unlike most NPS parks, this one is administered by state and local government entities.

Half of New Jersey’s dozen national parks are historic sites and areas, fitting for one of the original 13 Colonies.

The state’s other National Scenic & Recreational River that is a national park is the lower Delaware River just above Trenton, another estuary typically taken for granted but the largest free-flowing river in the eastern United States, says the park service.

The Great Egg Harbor River has some pretty impressive numbers itself — meandering 59 miles from its start as a trickle near Berlin in Camden County. Counting its tributaries, the river system has 129 miles of flowing water. Its watershed is 304 square miles of pristine wetlands, mostly in the heart of the Pinelands National Reserve, another of the state’s national parks.

The river offers many recreational opportunities. The park service lists backpacking, biking, bird watching, boating, camping, fishing, hiking, hunting, kayaking, nature walks, stargazing and wildlife viewing. But because these and more activities are spread across so many miles, the park’s identity is as tough to grasp as its water flowing to the Atlantic.

Fortunately, government agencies and nonprofit organizations have been effective at protecting this valuable public resource. Last month the state Department of Environmental Protection and the Nature Conservancy announced they had purchased another 1,155 acres of the Great Egg’s watershed — mostly where it flows toward Lake Lenape in Mays Landing. Most of the $2.9 million purchase was funded under the state’s Green Acres Program.

Atlantic County is helping a little too, matching a $25,000 Green Acres grant to purchase nearly an acre of flood-prone land in Mays Landing. The property will become a small park in Hamilton Township.

Such little and big pieces of preserved land in New Jersey add up, making it a national leader on a percentage basis.

An analysis by the U.S. Geological Survey in 2011 found that 18.4 percent of New Jersey is permanently protected natural land with a mandated management plan — quite a bit more than any other state in the East and any other mid-sized to small state. Only Alaska and California, with vast acreage available to them, have protected a higher percentage.

It’s an impressive accomplishment for this small state in the midst of the Northeast megalopolis, and a big contributor to the quality of life now and for future generations.