William Clayton was a clerk to Brigham Young and a member of the original 1847 party of Mormon pioneers to travel to the Salt Lake Valley. He was charged with the responsibility of keeping a log of trial conditions and distances to be used by future parties of Saints. The redundancy of counting wagon wheel revolutions in order to measure trail distances led him to the invention of the odometer. In 1848 he published his notes on the trail as The Latter-day Saints Emigrants' Guide, used by both Mormon and non-Mormon parties as a source of information for the westward trek.

In his honor, this branch of Poison Spring Creek is known as "William Clayton Slough". I'm not sure Brother William would see it as an honor. His description (from the Emigrants' Guide) of this place is "This ought to be avoided as a camping ground...The land exceeding miry, and smells bad." (See p.14 of the guide in the link above.)