Interest in a National Park Service unit at Aniakchak was renewed in the 1960s. In 1964, newly appointed Park Service director George B. Hartzog Jr. initialed a study of Alaskan lands titled Operation Great Land. The study recommended protection of Aniakchak. Further studies supported the report's recommendations. In the interim, the Aniakchak caldera was designated a national natural landmark in August 1970. In 1971 the Alaska Native Claims Settlement Act (ANCSA), which established a framework for the disposition of federal lands in Alaska. The process dictated by ANCSA required agencies to withdraw lands which they felt they should administer. The Park Service withdrew around Mount Aniakchak in 1973. The same year a Aniakchak Caldera National Recreation Area was proposed, extending to both sides of the peninsula and including Port Heiden on Bristol Bay. Opposition from native groups and the presence of mining claims on some lands forced a scaled-back plan for Aniakchak Caldera National Monument that, at , was close to the present area. At about the same time the Aniakchak River was nominated for the National Wild and Scenic Rivers System.