The nation's federal and tribal lands hold a record of thousands of years of human life. Historic preservation laws require government agencies to survey for sites eligible for the National Register of Historic Places, which bestows some protection against looting, vandalism, and other forces. As of 1997, however, only about 11 percent of the acreage had been surveyed-as reported by the Secretary of the Interior's Report on the Federal Archeology Program-which shows the enormity of the job.

Besides surveys, agencies conduct archeology in advance of highway building, leasing land to loggers, and other federally funded or licensed projects. Usually, excavation is carried out only when such work will damage a significant site. There are unanticipated discoveries too, such as a 500-year-old fishing trap found by a college naturalist class hiking in Alaska's Tongass National Forest.