This painting, by the American artist Frederic Remington (1861-1909), was used for the design of the window now on display in the Manitoba Museum.
Remington attempted many versions of "The Buffalo Runners, Big Horn Basin" and ultimately declared himself satisfied with one completed in 1909, the year of his death.
There are two notable modifications in the stained glass version by McCausland. He has made a mirror-image representation of the original, causing the furious motion of the scene to reverse direction, moving from left to right.
And McCausland's lavishly coloured floral embellishments are absent from most or all of Remington's own versions. Rich ground foliage was characteristic of the McCausland studio, and can be found in hundreds of their religious and secular windows made well into the 20th century.
More on Remington's fascinating life is here: http://en.wikipedia.org/wiki/Frederic_Remington