On a November morning in 1864, U.S. Army Col. John Chivington and 700 half-drunk volunteers attacked and massacred nearly 200 Cheyenne and Arapahoe Indians -- most of them women and children -- encamped along a dry wash in southeastern Colorado, just north of Lamar.

This debacle, known as the Sand Creek Massacre, served as a catalyst for two decades of bloodshed that decimated the Cheyenne and Arapahoe and left a legacy of bitterness among Native Americans that endures.

In 1999, in a bill sponsored by Sen. Ben Nighthorse Campbell (R-Colo.), a Northern Cheyenne, Congress directed the National Park Service to find the exact location of the massacre and survey it with a view toward making it a National Historic Site.

The job fell to staff archaeologist Doug Scott, of the Park Service's Midwest Regional Center in Omaha. Volunteers had searched before, but had not found the encampment. "Either the stream had buried it in silt and soil, or it had washed away, or we were looking in the wrong place," Scott said.

Scott, the Park Service's Great Plains team leader, is one of at least 600 and as many as 900 archaeologists working for the federal government. Nobody knows exactly how many there are, because many are seasonal and contract hires.

While archaeologists may not seem to fit into the button-down federal bureaucracy, the agencies need them. The Park Service alone has 60,000 sites -- that it knows about. There are storied tourist attractions such as the Gettysburg battlefield and the Indian ruins at Mesa Verde, but the portfolio also includes tiny spots like the Native American campsite at Gates of the Arctic on Alaska's North Slope.

And these known points of interest cared for by the Park Service say nothing about the chance encounters that occur whenever a government agency bulldozes a right-of-way, paves a runway, lays a foundation, makes a repair or digs a tunnel.

"At one point 10 years ago, there was a problem with moisture below the foundation of the house where Lincoln died, across the street from Ford's Theater," said the Interior Department's Frank McManamon. "We pulled up the boards and found a bunch of artifacts."

McManamon is the Park Service's chief archaeologist, but he also serves as consulting archaeologist for the parent Interior Department, point of contact for archaeologists throughout the federal government who may need anything from legal advice to a fresh set of eyes.

The Army Corps of Engineers, with a formidable archaeological staff of its own, called on Interior in the late 1990s to organize investigations to determine whether Kennewick Man, the remains of a middle-aged man who died 9,200 years ago, qualified as Native American. The Interior Department said he did, giving tribes an early victory in a bitter, still-unresolved battle with researchers seeking the right to examine the remains.

More recently, McManamon's office has been informally reviewing the research on more than 600 sets of human remains and other material from an 18th-century African American burial ground unearthed by the General Services Administration during construction of a federal office building in Lower Manhattan.

In all, the federal government produces about 20,000 archaeological reports a year, and McManamon is trying to log them in to the National Archaeological Database. Right now the database has 240,000 citations, but the work moves in fits and starts on an $800,000 annual budget.

McManamon said most of the logged items are surveys rather than actual excavations, "in part because we're not trying to destroy sites, as in the past." McManamon is a leading exponent of the modern creed that reminds archaeologists to be careful what they excavate, because "once you dig it up, it's gone."

For Scott in Colorado, the task was to find a site that existed but which had been covered over and forgotten for more than 130 years. The team knew it was close, but even an error of a few hundred yards in an area of pristine pastureland can condemn an archaeologist to months of futility.

Scott said his researchers started from the premise that earlier expeditions were looking for the site of the massacre in the wrong place. Then historians in the group huddled with aerial photographers and came up with a plausible alternative to the traditional site, about a mile to the north.

"In the spring of 1999, we started to check with metal detectors," Scott said. "About seven-tenths of a mile north of the traditional area, we started to run into cannonball fragments, bullets, kettles and cast-iron skillets, tools, scrapers and arrowheads."

With evidence of both an Indian encampment and military hardware, the team members felt they had found the right spot. "We didn't dig it all up," Scott said, "but we collected over 400 artifacts and worked about 3 1/2 miles of stream several hundred meters on either side."

The site squared with historical accounts: "There is nearly no evidence of resistance by the Arapahoe and Cheyenne," Scott said. "The overwhelming amount of material is from the Colorado Volunteers."

The team found pieces from a half-dozen 12-pound fragmentation shells fired from four mountain howitzers brought along on mules by Chivington's men to rip the encampment apart.

On Oct. 31, 2000, President Bill Clinton signed a bill authorizing creation of a National Historic Site at Sand Creek, 50 miles north of Lamar and 150 miles southeast of Denver.

Many archaeologists are employed by the National Park Service, which has at least 60,000 sites. Here, at the Little Bighorn Battlefield National Monument, they are working to protect the site during construction nearby.Archaeologist Doug Scott uses a transit in search for the site of the 1864 Sand Creek Massacre of Cheyenne and Arapahoe in southeastern Colorado.