 He moved to field assignments at Great Smoky Mountains and Rocky Mountain National Parks, and then made his name advancing the Gateway Arch project as superintendent of Gateway Arch National Park (then known as Jefferson National Expansion Memorial) from 1959 to 1962.After briefly leaving the service Hartzog returned as associate director in 1963 with the promise of succeeding Conrad Wirth in January 1964.As Director, he served as Stewart Udall’s right arm in achieving a remarkably productive legislative program that included 62 new parks, the National Historic Preservation Act of 1966, and the Bible amendment to the Alaska Native Claims Settlement Act that led to establishment of the Alaska parks.