retreat. North Cascades National Park is almost entirely protected as wilderness, and so the park has few structures, roads or other improvements. Visitors wishing to drive to a campground must do so in the adjacent national forests or national recreation areas. Camping inside the park requires hiking in by trail, horseback or boat, and camping is regulated by a permit system to ensure the wilderness is not over-exploited. Mountaineering is popular in the park and only unobtrusive clean climbing is allowed. Human history Paleoindians and Native Americans Human history in North Cascades National Park and the surrounding region begins 8–10,000 years ago, after the end of the last glacial period. Paleo-Indians slowly advanced from Puget Sound into the interior mountain region as the glacial ice retreated. Archaeological evidence from other sites hundreds of miles away from the park indicate that Hozomeen chert, a type of rock well-suited to the fabrication of implements, was mined from near Hozomeen Mountain, just east of the park border, for the last 8,400 years. Tools such as microblades made from Hozomeen chert are part of the archaeological record throughout the Skagit River Valley, west of the park and in regions to the east. Prehistoric micro blades 9,600 years old have been discovered at Cascade Pass, a mountain pass that connects the western lowlands to the interior regions of the park and the Stehekin River Valley. The microblades are part of an archaeological assemblage that includes five distinct cultural periods, indicating that people were traveling into the mountains nearly 10,000 years ago. As well as the archaeological excavation at Cascade Pass, there are another 260 prehistoric sites that have been identified in the park. When white explorers first entered the area in the late 18th century, an estimated thousand Native American Skagits lived in what is now North Cascades National Park as well as the surrounding area. Residing mainly to the west of the park near Puget Sound, the Skagits lived in settlements, culling their needs from the waterways and traveling by canoe. Skagits formed a loose confederation of tribes that united if threatened by outside tribes such as the Haidas, who lived to the north. They erected large houses or lodges that could house multiple families, each with their own partitioned area and entrance. The lodges were in length and in width, and the roofs were shed-styles, with a single pitch; structures built by other