Another landmark on the Wyoming portion of the Oregon Trail is Devil's Gate. Although the name sounds ominous, this was a welcome stop along the trail, because the fissure in the rock was created by the Sweetwater River.
If you've traveled through central Wyoming, you know it's a mostly arid region, making the presence of a river and the fresh water it provided a reason for the pioneers to give thanks.
As for the origin of the name, here's a link with a possible explanation.