The AEC researchers, driven in part by the belief that it must be possible to use the awesome power of an atomic explosion to help people and not just to kill them--hence the name, "Project Plowshare"--and in part by the need to keep large, expensive national laboratories busy in peacetime, developed plans to use underground nuclear explosions to dig a sea-level canal.  The idea was to blast a row of craters all the way across the isthmus.  Some minor (!) side effects were anticipated:  radioactive fallout, the possibility of earthquakes, and the need to displace a native population of about 40,000.  There was also concern about the ecological damage that might result from the free mixing of plants and fish between the Atlantic and Pacific Oceans through a sea-level canal. Ultimately, however, it was the public concern about nuclear testing and the 1963 Limited Test Ban Treaty that prevented these plans from going ahead.

Other nuclear landscaping ideas that were explored included Project Chariot, which involved using a nuclear explosion to dig a harbor near Cape Thompson, Alaska.  This idea, which was first proposed in 1957, was abandoned about five years later due in part to public objections.  A key proponent was physicist Edward Teller, known as the "father of the hydrogen bomb," who, on a tour of Alaska in 1958, spoke of "engaging in the great art of geographic engineering, to reshape the earth to your pleasure," and boasted that the AEC could "dig a harbor in the shape of a polar bear, if required."  (Quoted in "Project Chariot: Nuclear Legacy of Cape Thompson," by Douglas L. Vandegraft.)  

Such technological hubris sounds preposterous in today's world.  Most people would probably regard that as progress.

Links:
= highly recommended

"Special Reports--Bombs for Peace:  The Plowshare Pardox."  An excellent collection of articles by Glenn Roberts, Jr., photos, film clips, and links on Project Plowshare from InsideBayArea.com.

"'Peaceful' Nuclear Explosions," Scientific American (June 1996).  Focusing on China's interest in nuclear excavation technology, this article also looks at its history in some depth.

"Researching Atoms for Peace," based on an interview with Luke Vortman, a participant in Project Plowshare, this article was produced by the history program at Sandia National Laboratories.

The Legacy of Project Chariot.  A lengthy, detailed history, with illustrations.

"A Short History of the Laboratory at Livermore," by Bart Hacker, Science & Technology Review [Lawrence Livermore National Laboratory] (September 1998).  Includes extensive discussion of Project Plowshare, in which the lab was deeply involved.       

"'Sedan' tested use of nuclear explosives to move earth," from the Department of Energy's Nevada Operations Office (November 1, 1999).

Description and short clips from an official government film about Project Plowshare.   Clips play on RealPlayer. 

"The Plan to Nuke Panama," by Benjamin Ryder Howe, American Heritage of Invention and Technology (Spring 2002).  "For a monumental civil-engineering job, why not use the most powerful explosive of all?"

Field trip to the Nevada Test Site (NTS), Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ.  Part of a site associated with a 1995 student field trip, this page contains information and photos about the history of the NTS, including Project Plowshare.

"Nuclear Notebook: Soviet Nuclear Testing, August 29, 1949–October 24, 1990."  From The Bulletin of the Atomic Scientists. The U.S.  was not the only country that investigated peaceful nuclear explosions (PNEs).  This article provides a chronology of Soviet nuclear tests, including discussion of its PNE program.

The Atomic Century.  Sponsored by DOE's Argonne National Laboratory, this site includes timelines, historic documents, photos, and other material associated with the U.S. nuclear R&D and testing program, including Project Plowshare.