Wilderness with a capital W refers to a special landscape set aside by Congress to be managed for wildness, uninhabited by humans, and retaining its primeval character and influence. The idea of preserving Wilderness was developed by Aldo Leopold while he was a Forest Ranger on the Gila National Forest in the 1920's, and like Theodore Roosevelt before him, he believed that human development in wild landscapes harmed the health and well-being of all living creatures. People need wild areas as much as plants and animals, as places to challenge physical and mental abilities, awaken the soul, and connect spiritually. In 1964, the Wilderness Act was passed to designate wild areas and exclude development from unmodified landscapes, with the intent of preserving primitive environments as both retreat and reserve, providing solitude and tranquility now and into the future. Keeping Wilderness wild requires people working together to preserve the primitive environment by following wilderness regulations and Leave No Trace principles. The Sandia Mountain Wilderness, designated by Congress in 1978, forms the heart of the Sandia Mountain Range and the iconic image of Albuquerque's skyline; it covers 37,877 acres, and nearly one million people live at its base, many seeking solitude along its 117 miles of trails.