- Uinta Basin, near Cottonwood Springs, Little Mt.1
- Uinta Mountains; S.E. slopes. Mt. Emmons1
- Uinta Mts.1
- Uintah4
- Uintah & Ouray Indian Reservation (Hill Creek extension) Florence Creek, area around Big Spring.2
- Ulm, roadside park at east edge of town.1
- Ulster7
- Umiat, Colville River.1
- Umiat.2
- Unalaschka I.1
- Uncharted Hill Seep. 0.55 mile southeast of Illinois Power Plant, west side of & above the west Fork of the Vermilion River. Danville NW 7.5 minute topo.1
- Under power lines ½ mi. S.W. of the McKinley bridge ca. 8 mi. E. of town of Mio. Mentor Twp.1
- Under railroad trestle n. of Wolf Cr., e. of Bent Oak Hwy., Adrian.1
- Unga I., Shumagins.1
- Unicoi1
- Union51
- Union.1
- United States Highway 167 5.0 miles south of Saline County. Hurricane Creek.1
- United States Highway 71 at Sulphur.1
- Univ. of Missouri Bradford Farms, ca. 2 mi. SE of the inter. of WW & Olivet Rd. Just east of Columbia. Millersburg 7.5' Quad.1