Lookout SummitâÂÂofficially listed as "Lookout" in the Geographic Names Information SystemâÂÂis the highest point in Benton County, in the U.S. state of Washington. The mountain is also the highest point in the Rattlesnake Hills, with an elevation higher than the neighboring, more-well-known Rattlesnake MountainâÂÂwhich is the second highest peak in the range (as well as the county).