O
| Train Name | Railroad | Train Endpoints | Operated |
|---|---|---|---|
| Ohio Special | New York Central | Detroit, Michigan-Cincinnati, Ohio | |
| Ohio State Limited | New York Central | New York, New York-Cincinnati, Ohio | |
| Oklahoma Rocket | Rock Island Lines | Kansas City, MO-Oklahoma City, OK | 1950 |
| Oklahoman | St. Louis-San Francisco | St. Louis, Missouri-Oklahoma City, Oklahoma | 1965-1967 |
| Old Dominion | Richmond, Fredericksburg & Potomac | Washington, D.C.-Richmond, Virginia | 1947- |
| Olympian | Milwaukee Road | Chicago, Illinois - Seattle, Washington | May 28, 1911 - January 28, 1947 |
| Olympian Hiawatha | Milwaukee Road | Chicago, Illinois - Seattle, Washington | January 29, 1947 - May 22, 1961 |
| Orange Blossom Special | Seaboard Air Line Railroad | New York City - Miami | 1925-1953 |
| Oregonian | Oregon & California Southern Pacific |
San Francisco, California-Portland, Oregon-via Siskiyou Line | 1887-1926 |
| Oriental Limited | Great Northern | Chicago, Illinois - Seattle, Washington | 1905-1931; 1947-1951 |
| Orleanean | Missouri Pacific | New Orleans, Louisiana - Houston, Texas | |
| Overland Flyer | Union Pacific | 1887-1890 | |
| Overland Limited | Union Pacific | 1890-1963 | |
| Owl | Lackawanna | Hoboken-Buffalo | |
| Owl | New Haven | New York, New York (Grand Central)-Boston, Massachusetts | |
| Owl | Southern Pacific | San Francisco, California-Los Angeles, California | |
| Ozarker | Missouri Pacific | St. Louis, Missouri-Fort Worth, Texas | |
| Ozark State Zephyr | Chicago, Burlington & Quincy |
Read more about this topic: List Of Named Passenger Trains Of The United States (N-R)