In February 1930, Marshall published an essay, after it was rejected by four magazines. This is now celebrated as a defense of wilderness preservation, and the essay expanded themes developed in his earlier article, "The Wilderness as a Minority Right." Published in "The Scientific Monthly," the essay is considered one of Marshall's most important works. He argued that wilderness was worth saving not only because of its unique aesthetic qualities, but because it could provide visitors with a chance for adventure. Marshall stated: "There is just one hope of repulsing the tyrannical ambition of civilization to conquer every niche on the whole earth. That hope is the organization of spirited people who will fight for the freedom of the wilderness." The article became a much-quoted call to action and by the late 20th century was considered seminal by wilderness historians.