Who is Art Croft from The Ox-Bow Incident and what is their importance?

Art Croft is a cowboy who has just come into Bridger's Wells after spending the entire winter alone with Gil Carter as they watched over a herd of cows. Art is a cautious man who does nothing to extreme, a contrast to his heavy drinking, fight loving partner. In fact, the reader is left with the impression that Art often appoints himself babysitter of his partner to avoid the trouble Gil can sometimes get into.