A prolific landscape record evolved as soon as cameras and equipment could be reliably used outdoors. Most nineteenth-century photographers worked on government-sponsored surveys. Others helped to lure investors westward with the images they made along the routes of the railroads. At the same time, Americans were hanging framed images by such photographic artists as Carleton Watkins and Eadweard Muybridge on their parlor walls. Photographs of unspoiled national treasures such as those by Ansel Adams exerted considerable influence on the federal government’s efforts to create national parks. Modern and contemporary photographers have recorded their impressions of both man’s and nature’s impact on the land, from Robert Dawson’s images of polluted waterways to Emmet Gowin’s views of the aftermath of Mount St. Helens’s spectacular eruption.