In the 1930s, three state parks were established in the Loess Hills. More than 10,000 acres in the northern part of the range were included in the National Registry of National Landmarks in 1986. Through the effort of multiple public agencies, local communities and private organizations, the Loess Hills Scenic Byway was established through the heart of the hills formation in the 1990s. A part of the byway passes near the center. In 2000 the route was designated as a National Scenic Byway by the Federal Highway Administration. In 1995, the Natural Resources and Conservation Service of the US Department of Agriculture undertook a study that showed that nearly 85,000 acres of Loess Hills contains natural and cultural resources of critical importance. Four years later, the Iowa legislature formed the Loess Hills Alliance, a broad, grass-roots organization composed of representatives from each of the seven counties in the Loess Hills. Their charter is to promote the protection of the hills. In 2002, the National Park Service published the results of a survey and study of the region undertaken at the direction of Congress to evaluate the Loess Hills for possible designation as a unit of the National Park System. While a majority of the cross section of interviewees in the seven affected counties agreed with federal land purchase for a national park, the landowners in the northerly four counties strongly disagreed. Since then, state and private conservation groups along with concerned landowners, have been the main actors in securing Loess Hills lands for protection.