Granite Staters may not have heard of the federal Land and Water Conservation Fund, but they probably have enjoyed using the public and recreational lands it has helped acquire and protect.

The program, which is more than 50 years old, is in peril unless Congress acts by the end of next month.

“The future is in jeopardy. The program is operating under three year reauthorization that expires on September 30,” Rep. Annie Kuster highlighted Thursday at an event to mark the 100th anniversary of the establishment of the White Mountain National Forest and to spotlight the threat facing the conservation fund.

The conservation fund has been used for dozens of projects in recent years including the proposed Merrimack River Greenway Trail in Concord, as well as improvements to Terrill Park.

The fund was created to promote outdoor recreation and conservation. It works as a federal 50/50 matching grant program, with state and local governments picking up half the costs of a project.Amy Lindholm, a coalition manager for the fund, said it has helped support the White Mountain Trailhead Partnership, which invested $9 million over the years to acquire 14,000 acres of land, much of it used to protect access to popular trails that had crossed through privately held property.

Its supporters highlight that it uses no taxpayer dollars, with the money instead coming from the revenues and royalties from energy development on federal lands.

“In New Hampshire we’ve seen tremendous benefit from the Land and Water Conservation Fund, bringing grant funding to establish parks, river walks, forest land expansion, and so many other projects,” Kuster said.

The three-term Democrat who represents the state’s 2nd Congressional District was joined by conservationists at an event at Plymouth State’s Museum of the White Mountains that was organized the New Hampshire chapter of League of Conservation Voters, an environmental advocacy group.

Officials pointed out that the White Mountains National Forest receives more visitors per year than the heavily visited Yellowstone or Yosemite National Parks.

Alex Taurel, conservation program director at the League of Conservation Voters, warned that if the fund expires, “it’s going to make it harder to create more parks and provide the same sorts of recreational opportunities that we want our kids to have that we’ve been able to enjoy.”

“We need more parks. We’ve got a growing population that needs more places to play, hike, camp, fish and hunt,” Taurel said.

Matt Leahy, public policy manager for the Society for the Protection of New Hampshire Forests, said no current projects will suffer if Congress does not reauthorize the fund, but said the concern is what happens after this year and “those projects that are not yet in the hopper.”

Kuster said Republican leadership that controls the House has yet to introduce a bill that would reauthorize the fund for another three years.

Many western Republicans, who have fought the federal government’s role in making land decisions, oppose the fund because they see it as another overreach of a federal program impinging on their private property rights. The program briefly expired in 2015, before it was reauthorized by Congress.

Kuster (along with Congresswoman Carol Shea-Porter) is a co-sponsor of a bipartisan House bill to permanently reauthorize the fund. She said the measure has 232 sponsors (including 38 Republicans), which is more than the 218 needed to pass a bill in the House. “We cannot allow partisan politics to get in the way protecting our environment,” she said.