President Obama turned a vast stretch of Maine woods into the nation’s newest federal parkland on Wednesday, siding with conservationists who want the wild lands protected, over residents and officials who oppose intrusion from Washington and restrictions on use of the land.

Mr. Obama designated more than 87,500 acres of rugged terrain, donated by a founder of the Burt’s Bees product line, as the Katahdin Woods and Waters National Monument, administered by the National Park Service, a day before the service’s 100th anniversary. It became by far the largest region of federal parkland in Maine, surpassing the 48,900-acre Acadia National Park on the coast.

It takes an act of Congress to create a national park, but under a 1906 federal law, the Antiquities Act, a president can act unilaterally to establish a national monument, a power that Mr. Obama has used to build a major part of his environmental legacy. He has created two dozen national monuments, more than any previous president, ranging from small sites like the Stonewall Inn, a gay rights landmark in Manhattan, to more than 300,000 acres in the mountains east of Los Angeles.

The designations prevent new mining and drilling operations, and sometimes curtail logging, grazing, road-building, hunting and recreation — limits that in some rural areas, particularly in the West, are bitterly resented by residents and business people who say their regions’ economies depend on use of the land. Advocates say the monuments can actually generate economic activity and jobs, through tourism and recreation.