During the 1930s, Adams began to deploy his photographs in the cause of wilderness preservation. He was inspired partly by the increasing incursion into Yosemite Valley of commercial development, including a pool hall, bowling alley, golf course, shops, and automobile traffic. He created the limited-edition book "Sierra Nevada: The John Muir Trail" in 1938, as part of the Sierra Club's efforts to secure the designation of Kings Canyon as a national park. This book and his testimony before Congress played a vital role in the success of that effort, and Congress designated Kings Canyon as a national park in 1940.