 When the traders of Hudson's Bay Company first visited the Mandan Indians in 1790 they found that tribe possessed tublike boats with framework of willow poles, covered with raw buffalo hides.Later, frontiersmen who ascended the Missouri River noted this light, convenient craft.From 1810 to 1830, American fur traders on the tributaries of the Missouri regularly built boats eighteen to thirty feet long, using the methods of construction employed by the Indians in making their circular boats.