After Washington D.C.
Stewart L. Udall's legacy and stewardship of the Department of the Interior during the course of two presidential administrations would continue to influence environmental policy into the latter decades of the twentieth century and beyond.
However, Stewart's golden years were anything but quiet, and involved numerous projects and initiatives related to his love of the environment and his respect for the original inhabitants of the continental United States.
Stewart's subsequent work through the 1970s to the 2000s was incredibly varied and a testament to his lifelong concern for the environment, energy conservation, and the conditions of Native American affairs.
He served as campaign manager for his brother Morris K. Udall's unsuccessful (but highly lauded) Democratic presidential nomination campaign between 1975-1976, where Morris, even with only a little over 10% of the delegate votes at the primaries, still came out second place to Jimmy Carter.
Stewart's work would include advocating for Diné uranium miners in the 1983 Begay Trial in Phoenix, AZ; organizing an expedition along the Coronado Trail for Heard Museum members; serving on the Central Arizona Water Conservation Board; joining the advisory board for the Institute for Resource Management; and conceiving/manifesting numerous planned conferences on energy conservation, the environment, and Native American affairs.
Stewart L. Udall would continue to to make contributions as an environmental author, consultant, lawyer, and advocate for cultural preservation, particularly within the U.S. southwest.
His work in those capacities lasted well into the mid-1990s and early 2000s before his death in 2010; and his accomplishments and spirit live on in the form of the Morris K. Udall & Stewart L. Udall Foundation, which provides scholarships and grants to qualifying students seeking careers in environmental science and law, as well as to Native American students seeking careers in health care and tribal law.
Stewart's authorship expanded exponentially during his later years following his resignation as Secretary of the Interior. Following his 1963 publication of his environmental manifesto The Quiet Crisis, Stewart published:
- 1979: Agenda for Tomorrow (1968): positing that cities be considered as environments and urban cleaning become a national project.
- America's Natural Treasures: National Nature Monuments and Seashores (1971): a vivid photographic essay on U.S. national parks, national monuments, and nature reserves.
- The Energy Balloon (1974): Co-authored with Charles Conconi & David Osterhout, a detailed analysis and apologia of wasteful U.S. energy habits and steps needed to correct them.
- To the Inland Empire: Coronado and our Spanish Legacy (1987): a retracing of the trails of Spanish colonizer Francisco Vásquez de Coronado as he searched for the "golden cities" of Cibola in what is now Arizona, New Mexico, Oklahoma, and Texas. Stewart was bestowed knighthood for this book by King Juan Carlos of Spain (r. 1975-2014) in 1989.
- The Quiet Crisis and the Next Generation (1988): A revision of 1963's The Quiet Crisis featuring nine new chapters.
- Beyond the Mythic West (1988): Co-authored with Patricia Nelson Limerick & Charles F. Wilkinson, an examination of change upon the inhabitants and land of the western U.S.
- In Coronado's Footsteps (1991): A collaboration with photographer Jerry Jacka, this work examines Francisco Vásquez de Coronado's colonial exploration of the U.S. southwest.
- Arizona, Wild & Free (1993): Co-authored with Stewart's nephew Randy Udall & the Arizona Game & Fish Department, a look at Arizona's wilderness areas and habitats.
- National Parks of America (1993): Featuring photographs by acclaimed landscape photographer David Meunch.
- The Myths of August: A Personal Exploration of our Tragic Cold War Affair with the Atom (1994): In which Stewart takes aim at the U.S. government's denial of the effects of fallout from atmospheric tests and the false attribution of cigarettes to lung cancer among uranium miners (in particular Diné uranium miners, for whom Stewart advocated in the 1983 Begay Trial in Phoenix, AZ).
- Majestic Journey: Coronado's Inland Empire (1995): A reissuing of 1987's To the Inland Empire with new photographs, map, and preface.
- The Forgotten Founders: Rethinking the History of the Old West (2002): Stewart's last book, a collection of essays advocating for the existence of a greater racial and gender diverity of people in the making of the U.S. Western expansion.