| Newcastle, Wyoming | Encyclopedia | Nicole Lebsack |
| Newspapers, Jackson Hole | Encyclopedia | Kerry Drake |
| Newspapers, Jackson Hole, photo controversy | Encyclopedia | Kerry Drake |
| Nichols, Lora Webb, photographer | Encyclopedia | Lori Van Pelt |
| Nicolaysen Art Museum & Discovery Center | Field Trips | |
| Nineteenth Amendment, ratification of by Wyoming | Encyclopedia | Rebecca Hein |
| Ninth Crossing, Sweetwater River | Encyclopedia | WyoHistory.org |
| Niobrara County, Wyoming | Encyclopedia | Nicole Lebsack |
| North Platte River Basin | Encyclopedia | Emilene Ostlind |
| North Platte River crossings; Oregon Trail sites of | Encyclopedia | WyoHistory.org |
| Northern Arapaho Tribe, 1905 Land Cession Agreement | Encyclopedia | WyoHistory.org |
| Northern Arapaho, arrival of on Shoshone Reservation, 1878 | Encyclopedia | WyoHistory.org |
| Northern Utilities, Casper Star-Tribune and | Encyclopedia | Kerry Drake |
| Nye, Bill, 1880s Laramie Boomerang editor and humorist | Encyclopedia | Charles E. Rankin |
| Obsidian Cliffs | Field Trips | |
| Occidental Hotel | Field Trips | |
| Odd Fellows Building, Casper | Encyclopedia | Stephanie Lowe |
| Oil business, early emigrant trails | Encyclopedia | Allan Fraser |
| Oil Fields, Five of Wyoming’s historic | Encyclopedia | Rebecca Hein |
| Oil refining, Wyoming | Encyclopedia | Tom Mast |
| Oil theft, Wind River Reservation | Encyclopedia | Marjane Ambler |
| Oil, history of in Wyoming | Encyclopedia | Phil Roberts |
| Okie, J. B. | Encyclopedia | Tom Rea |
| Old Faithful geyser, Yellowstone National Park | Field Trips | |
| Old Faithful Inn, Yellowstone National Park | Encyclopedia | John Clayton |
| Old West Museum | Field Trips | |
| Opal Hub, The | Field Trips | |
| Oregon Basin Oil Field | Encyclopedia | Rebecca Hein |
| Oregon Buttes | Field Trips | |
| Oregon Buttes, Oregon Trail landmark | Encyclopedia | WyoHistory.org |
| Oregon Trail Ruts | Encyclopedia | Wyoming State Historic Preservation Office |
| Oregon Trail Ruts | Field Trips | |
| Oregon Trail-Ferdinand V. Hayden Monument | Field Trips | |
| Osborne, Gov. John E., and Wyoming politics, 1892-1893 | Encyclopedia | Lori Van Pelt |
| Osborne, John | Encyclopedia | Wyoming State Archives |
| Ostrom, George, of Sheridan, World War I soldier and artist | Encyclopedia | Douglas R. Cubbison |
| Outfitting in Wyoming | Encyclopedia | Brian Beauvais |
| Overland Trail, defense of | Encyclopedia | Rebecca Hein |
| Overton, Carrie Burton. First African-American Female Student at UW | Encyclopedia | Kim Viner |
| Oyster Ridge Music Festival | Field Trips | |
| 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 |
