The Mellon Foundation plans to give the U.S. government more than 100,000 acres of historically and ecologically important land, including the Antietam Cornfield in Maryland, part of the site of the battle that produced more casualties in one day than any other in the Civil War.

In what is billed as the largest land donation ever to the government, Interior Secretary Manuel Lujan Jr. is scheduled on Tuesday to accept the deeds to the cornfield as well as 93,000 acres of wildlife habitat in North Carolina from the Richard King Mellon Foundation of Pittsburgh and the Arlington-based Conservation Fund.

The two organizations expect to give the Interior Department land at eight other sites as well as two additional parcels at Antietam over the next year. The proposed donation includes three sites in Virginia -- at the Shenandoah National Park and the Civil War battlefields of Wilderness and Five Forks -- and part of the Gettysburg, Pa., battlefield.

But before the Interior Department can accept some of these parcels, Congress must expand the boundaries of several national parks. Local governments and landowners often fight such boundary changes.

The Conservation Fund purchased the properties using $21 million from the Mellon Foundation, which has spent $170 million in the last 13 years to preserve land.

Officials with both organizations said that, in many cases, owners sold the land for less than market value in the interest of wildlife or historical preservation. The properties also include parcels in New Mexico, Colorado and Maine.

"Because of funding reductions, the {federal} agencies need help to acquire properties for parks and wildlife refuges," Mellon Foundation President Seward Prosser Mellon said in a statement released yesterday. "In some cases, particularly involving Civil War battlefields, where the threat of encroaching development is so great, prompt action by the private sector can make the difference."

Lujan called the gifts a "way to keep history alive" in an era when federal funds for land purchases greatly fall short of acquisition goals. Federal land acquisition funds fell to $17 million during the last year of the Reagan Administration, but have rebounded under President Bush to $250 million this year.

Later this month, Lujan is expected to unveil a joint federal-state plan to buy Civil War battle sites in 20 states, which an Interior Department spokesman called a significant switch from the government's piecemeal purchases of the past to a concerted effort at conservation.

The donation of 135 acres outside Fredericksburg, on the Wilderness battlefield, where generals Robert E. Lee and Ulysses S. Grant clashed for the first time, "is truly wonderful news for us," said Maria Burks, superintendent of the national park that includes that battlefield. "The Conservation Fund was able to move very quickly when we could not."

Congress included the parcel in a list of 1,800 acres it wants to buy in the area, but no appropriation has been made for the project.

One of the Virginia parcels, Five Forks, was the site of the April 1865 battle in which Lee lost 4,400 of his 10,600 troops. The battle, known as the "Waterloo of the Confederacy," paved the way for the surrender at Appomattox April 9, 1865. The 930-acre donation -- purchased for $930,000 -- will be an addition to the Petersburg National Battlefield and preserve virtually all of the battle site.

Shenandoah National Park, where park officials are concerned that development is destroying the views from Skyline Drive, will receive 1,287 acres in two separate parcels from Mellon.

Disposition of two of the three Antietam parcels and the Gettysburg site will remain in limbo until Congress decides whether to authorize Interior to accept them.

A bill to allow the Park Service to accept the Conservation Fund's 266 acres at Gettysburg is expected to pass Congress this summer, but Antietam neighbors have strongly objected to plans to expand that site.

Antietam was recently named one of the nation's 11 most endangered historic sites by the National Trust for Historic Preservation, in part because one-third of the parkland remains in private hands.

The donation to be announced Tuesday also includes land at:

Alligator River, N.C. The 93,000-acre gift will be combined with an adjacent refuge to form the Pocosin Lakes National Wildlife Refuge.

Forked Lightning Ranch, N.M. The 5,556-acre property, once owned by film actress Greer Garson, will become the part of the new Pecos National Historical Park.

Mackay Island National Wildlife Refuge, N.C., which will get 130 acres of upland territory near the Currituck Sound. The adjoining marshes are an important nesting ground for migratory birds.

Rachel Carson National Wildlife Refuge, Maine, which will receive 122 acres of wetlands and woodlands on Cutts Island.

Rocky Mountain National Park, Colo., which will receive 468 acres, to preserve a migratory path for elk.