More than 14,000 acres of expansive coastal lands that served as training grounds for generations of soldiers were declared a national monument Friday.

Fort Ord, a former military base just north of Monterey, will be the country's newest national monument and the second that President Obama has created under the 1906 Antiquities Act.

The federal nod will help the public lands, which hold more than 80 crisscrossed miles of hiking and cycling trails, gain prominence as a travel destination and protect the lands as an environmental refuge.

"We're truly overjoyed," said Michael Houlemard, executive officer of the Fort Ord Reuse Authority. "Yesterday we were Fort Ord Public Lands. Today we're Fort Ord National Monument."

The former military base, established in 1917, stretched east from the Monterey Bay dunes to inland agricultural fields over 28,000 acres - an area roughly the size of San Francisco. For decades, U.S. Army troops trained on the terrain, which is covered by both scraggly ice plants and lush grasses and oak trees.

When the base closed in 1994, much of the land was given back to the state. Some of the area became California State University Monterey Bay. A large portion was kept for public use and became a popular outdoor recreation area, while other parts of the land became a strip mall and affordable housing.

The 14,000 acres set aside to become Fort Ord National Monument are mostly on the eastern half of the former base. It's a sprawling expanse of land, and it took Houlemard years to explore every corner of it. More than 100,000 visitors venture into the area each year.

Half of the land is already under the stewardship of the Department of the Interior's Bureau of Land Management. The other half is barred from public use because it could still contain old unexploded ordnance from military years. The Army Corps of Engineers is cleaning up those lands and expects to have them ready for public use by 2019.

President Obama signed the official proclamation Friday, called the area "one of the crown jewels of California's coast," and praised its historical and environmental significance.

Local politicians and environmental groups such as the Sierra Club commended the president's decision and noted that the administration listened to strong support from local advocates and veterans who wanted to see the land protected.

The president has the power to designate national monuments without congressional approval from the 1906 Antiquities Act. Obama first used the act to designate the Fort Monroe National Monument in Hampton, Va., in 2011.