A grease trail is an overland trade route, part of a network of trails connecting the Pacific coast with the Interior in the Pacific Northwest. A trade route is a logistical network identified as a series of pathways and stoppages used for the commercial transport of cargo The British Columbia Coast is Canada 's western continental coastlines The British Columbia Interior or BC Interior or Interior of British Columbia, usually referred to only as The Interior, is one of the three main regions The Pacific Northwest is a region in the northwest of North America (the term refers to the land not the ocean Trails were developed for trade between indigenous people, particularly the trade in eulachon oil. For indigenous peoples in the United States other than Hawaii and Alaska see also Native Americans in the United States. The eulachon, also hooligan, ooligan, or candlefish, is a small anadromous ocean fish Thaleichthys pacificus, a Smelt The grease from these small fish could be traded for furs, copper, obsidian, among other things. Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Obsidian is a naturally occurring Glass formed as an extrusive Igneous rock. The Stóːlō people of the Fraser River simply ate the fish, either fresh or smoked, but the people of the interior used the oil as a condiment (similar to butter) and in various other ways. For other uses of this name see Fraser River (disambiguation. Butter is a Dairy product made by churning fresh or fermented Cream or Milk.