In October 1966, the United States Congress approved the National Historic Preservation Act. The law declared that "The spirit and direction of the Nation are founded upon and reflected in its historic heritage," and that "historic properties significant to the Nation's heritage are being lost or substantially altered, often inadvertently, with increasing frequency."
One part of the law
requires federal agencies to identify and protect important historic and
archeological sites, if they might be harmed by federally funded construction
projects.
Before any work begins, historic sites in the path of federally funded construction are identified and considered. The need to protect these sites is balanced along with environmental issues against the needs for safe and efficient transportation.
The State Highway 29 study is an example of how this process works, step-by-step and over a period of many years.