Tipis (French) or teepees (English) -- these are the two common spellings of the Sioux word that means "live" or "dwell" -- the tipi was ideally suited for the nomadic life of the Native Americans and it was perfectly suited as a dwelling for nomadic people in the harsh environments of the high plains buffalo country.
The conical shape of the tipi sheds wind loads from all sides and the narrow top allows for least resistance at the point where the wind is strongest. Rain and snow is shed easily. The number of poles used for the frame adds to the soundness of the structure while adding to the beautiful architectural design that is so admired. Tipis were originally made from animal skins; buffalo were preferred but elk was also used in mountain regions where bison were scarce. The switch to canvas came in the mid to late 1800's as bolts of military canvas became a standard trade item. Lighter in weight for tribes constantly on the move, canvas let more light in and was easier to construct than hide tipis. As the bison met their demise from the commercial trade in buffalo leather (ironically, used for military purposes in Europe and America) canvas became the only alternative at the end of the 19th century.