The US Federal Wilderness Act of 1964 was not vague about its intent: to protect significant and as-yet unspoiled land and wildlife habitat from the ravages of “an increasing population, accompanied by expanding settlement and growing mechanisation.” Humans could visit, but only under certain conditions, and they couldn’t stay permanently.

Preserving land and seeking to maintain it as close to its “natural condition” as possible required developing strict access rules: Everyone is welcome to trek through designated national wilderness areas provided they use their feet or those of horses or other pack animals. No motor vehicles or boats, nor “other form of mechanical transport” are allowed. Years later, the Americans with Disabilities Act made wheelchairs an exception.