The Watermark for Middleton shoudl be right around here at 37.1208147, -113.5407881, according to the GNIS/USGS: https://edits.nationalmap.gov/apps/gaz-domestic/public/search/names/1437636

or be on the north side of the freeway, according to the Washington County Historical Society Map, not on the south side: https://wchsutah.org/towns/middleton.php