Draw a line around a raw slice of wild land and leave it the hell alone. No roads. No hotels or visitor centers. No mechanized travel. Even in the country that invented national parks, it was a radical idea when Congress passed the Wilderness Act back in September 1964. That law—which many call our country’s most poetic and idealistic—marked a new era in conservation, with a new goal to aspire to, a new rallying cry, and a new and powerful tool to sculpt the American landscape into a shape just perfect for backpackers. And like the best ideas, this one is still sparking debates today. Excuse us while we celebrate.