| O’Bryan, Lowell, death of on UW campus, 1922 | Encyclopedia | Phil Roberts |
| Pacific Springs, stopping place on the Oregon Trail | Encyclopedia | WyoHistory.org |
| Paleon Museum | Field Trips | |
| Palette Ranch and Jack Creek Trailhead | Field Trips | |
| Parco (Sinclair) historic district | Field Trips | |
| Parco Museum | Field Trips | |
| Park County Archives | Field Trips | |
| Park County Fair | Field Trips | |
| Park County, Wyoming | Encyclopedia | Lynn Johnson Houze |
| Parker, J. P. and Martin Ringo, Oregon Trail graves of | Encyclopedia | WyoHistory.org |
| Parkitecture, Wyoming | Encyclopedia | John Clayton |
| Parrott, Big Nose George | Encyclopedia | Lori Van Pelt |
| Parting of the Ways | Field Trips | |
| Parting of the Ways | Encyclopedia | WyoHistory.org |
| Pathfinder Dam | Field Trips | |
| Pathfinder Dam | Encyclopedia | The National Park Service |
| Paul, Elizabeth, pioneer grave of | Encyclopedia | Randy Brown |
| Payton, E. T., journalist and mental patient | Encyclopedia | Rebecca Hein |
| PBS, Wyoming | Encyclopedia | Doug McInnis |
| Pedro II, emperor of Brazil, crosses Wyoming, 1876 | Encyclopedia | Phil Roberts |
| Pedro Mountain Mummy, The | Encyclopedia | Rebecca Hein |
| Penney, J. C. | Encyclopedia | Doug McInnis |
| Permanent Wyoming Mineral Trust Fund | Encyclopedia | Sarah Gorin |
| Petersen, Carol, Cokeville bombing oral history | Oral Histories | Wyoming State Archives |
| Philharmonic Orchestra of Casper | Encyclopedia | Rebecca Hein |
| Philippines, Wyoming Troops in 1898 | Encyclopedia | Douglas R. Cubbison |
| Pictographs and Petroglyphs | Encyclopedia | Tom Rea |
| Pictographs near Outlaw Canyon | Field Trips | |
| Piedmont Charcoal Kilns | Encyclopedia | WyomingHeritage.org, Wyoming State Historic Preservation Office |
| Piedmont Charcoal Kilns | Field Trips | |
| Pinedale Anticline and Jonah Field | Field Trips | |
| Pinedale Anticline development | Encyclopedia | Ann Chambers Noble |
| Pinedale, Wyoming | Encyclopedia | Ann Chambers Noble |
| Pipelines in Wyoming, a Historical Overview | Encyclopedia | Tom Mast |
| Pitchfork Ranch | Encyclopedia | Brian Beauvais |
| Platte Bridge Station, Battle of | Encyclopedia | Ellis Hein |
| Platte County, Wyoming | Encyclopedia | Nicole Lebsack |
| Point of Rocks Stage Station | Encyclopedia | WyomingHeritage.org, Wyoming State Historic Preservation Office |
| Point of Rocks Stage Station | Field Trips | |
| Poison Spring, Oregon Trail site of | Encyclopedia | WyoHistory.org |
| Pollock, Jackson | Encyclopedia | John Clayton |
| Pony Express route, central Wyoming | Field Trips | |
| Pony Express, Buffalo Bill and | Encyclopedia | Tom Rea |
| Post, Amalia grave | Field Trips | |
| Post, Amalia, women’s rights activist | Encyclopedia | D. Claudia Thompson |
| POW camps, World War II Wyoming | Encyclopedia | Cheryl O’Brien |
| Powder River Basin | Encyclopedia | Emilene Ostlind |
| Powder River Expedition, 1865 | Encyclopedia | Ellis Hein |
| Powell, John Wesley | Encyclopedia | Rebecca Hein |
| Powell, Wyoming | Encyclopedia | Jeremy Johnston |
