- Off County P near Bridge 10, Kickapoo River Area 6, Transect 17, Tree 1901
- Off Hwy 61, along Niobrara River south of Merriman1
- Ohio97
- Ohio and Minnesota1
- Ohio or Pennsylvania1
- Ohmer Creek Campground, Mitkof Island, south of Petersburg1
- Okaloosa1
- Okanogan1
- Okefenokee National Wildlife Refuge1
- Okefenokee Swamp, Minnie's Lake rest shelter1
- Oklahoma4
- Oktibbeha24
- Old John Lake1
- Old John Lake, Brooks Range2
- Old Man's Cave, Benton Township, ca. 6 mi. NE of South Bloomingville1
- Old Man's Cave, Benton Township, south-central part of Sect. 11, ca. 6 mi NE of South Bloomingville2
- Old Man's Cave, Benton Township, south-central part of sect. 11, ca. 6 miles NE of South Bloomingville1
- Old Peshtigo Road between Marinette and Peshtigo1
- Old Rag Fire Road on trail in Whiteoak Canyon, Blue Ridge Mountains, Shenandoah National Park1
- Old Rag Mountain1