The Wilderness Act of 1964 was written by Howard Zahniser of The Wilderness Society. It created the legal definition of wilderness in the United States, and protected 9.1 million acres (36,000 km²) of federal land. The result of a long effort to protect federal wilderness and to create a formal mechanism for designating wilderness, the Wilderness Act was signed into law by President Lyndon B. Johnson on September 3, 1964 after over sixty drafts and eight years of work.