Long before the arrival of Europeans, central and northern Yukon escaped glaciation as it was part of Beringia (Bering land bridge). Remains of human inhabitation were found near Old Crow appearing to be the oldest in North America. Around 800 AD, the volcanic eruption of Mount Churchill near the Alaska border blanketed southern Yukon with a layer of ash which can still be seen along the Klondike Highway. Coastal and interior First Nations already had extensive trading networks and European incursions into the area only began early in the 19th century with the fur trade, followed by missionaries and the Western Union Telegraph Expedition. By the latter end of the 19th century gold miners were trickling in on rumours of gold, creating a population increase justifying the setting up of a police force, just in time for 1897's start of the Gold Rush.