Three western House Democrats called for President Obama to use the Antiquities Act to create a new national monument in each of their states Tuesday, as the National Park Service nears its 100th birthday on Thursday.

Rep. Raúl Grijalva (D-Ariz.), the ranking Democrat on the House Natural Resources Committee, renewed his call for Obama to preserve a large swath of land around Grand Canyon National Park. Rep. Dina Titus (D-Nev.) promoted the idea of a monument in the Gold Butte area of southern Nevada. And Rep. Beto O’Rourke (D-Texas) called for the Park Service to incorporate an old U.S. Army artillery range, left unused since 1966, at Castner Range, in El Paso.

League of Conservation Voters President Gene Karpinski told reporters on a conference call he is “cautiously optimistic” about the potential creation of a national monument in Maine Woods, a proposed 87,000-acre area in Maine.

The lawmakers acknowledged that conservation advocates aren’t likely to see Congress pass legislation creating new national parks, so they’re calling on Obama to use the controversial Antiquities Act, which allows the president to establish large portions of land as monuments without Congress’s consent. Since taking office, Obama has set aside 260 million acres of land and water as national monuments, according to the White House.

Grijalva was particularly critical of Republicans in Congress for opposing the creation of new parks.

“Under more normal situations, under situations in which facts and science would be predominant in decision making, these areas would have been considered logically to be part of a designation,” Grijalva said on the conference call.