List of reporting marks: U

U

 * UBTX - Union Camp Corporation
 * UCCX - Union Carbide Canada, Ltd.
 * UCEX - Union Electric Company
 * UCFX - Union Carbide Corporation
 * UCLX - Vulcan Minerals Company
 * UCOX - Union Carbide Corporation
 * UCPX - Essem Corporation
 * UCR - Utah Coal Route
 * UCRY - Utah Central Railway
 * UELX - United Equipment Leasing Associates; Archer Daniels Midland
 * UECZ - Union Elevator Co.
 * UEEZ - Union Equity Elevator Co.
 * UEFZ - Union Equity
 * UFIX - Utility Fuels, Inc.
 * UIWX - Riley Stoker Corporation
 * UMP - Upper Merion and Plymouth Railroad
 * UMPX - Upper Merion and Plymouth Leasing Company
 * UNI - Unity Railways
 * UNCX - Union Carbide Canada, Ltd.
 * UNPX - Procor
 * UNSX - Unitrain Services
 * UO  - Union Railroad (Oregon)
 * UOCX - General American Transportation Corporation
 * UP  - Union Pacific Railroad
 * UPAX - United Power Association
 * UPB - Union Pacific Railroad
 * UPFE - Pacific Fruit Express; Union Pacific Railroad
 * UPM - Union Pacific Railroad (Milwaukee Road directed operations)
 * UPOZ - United Parcel Service
 * UPP - Union Pacific Railroad (passenger cars)
 * UPRQ - Union Pacific Railroad End Of Train Devices
 * UPRX - Union Pacific Fruit Express Company
 * UPS - Union Pacific Railroad (slugs)
 * UPSZ - United Parcel Service
 * UPT - Union Pacific Railroad (fuel tenders)
 * UPWZ - United Parcel Service
 * UPX - Union Pearson Express
 * UPY - Union Pacific Railroad (yard switchers)
 * URDX - United States Steel
 * URR - Union Railroad (Pittsburgh, Pennsylvania)
 * URTX - Union Refrigerator Transit Line; General American Transportation Corporation
 * URY - Union Railway of Memphis
 * USAX - United States Army
 * USBX - GE Rail Services
 * USCX - William G. Simon
 * USEX - Evans Railcar Leasing Company
 * USFU - United States Air Force
 * USGX - Union Sugar Company
 * USIX - US Industrial Chemicals Company
 * USLF - Burlington Northern Railroad
 * USLX - Evans Railcar Leasing Company; GE Capital Railcar Services
 * USNX - United States Navy
 * USPX - US Plastics Corporation
 * USRX - U.S. Railways, Inc.
 * USSX - United States Steel
 * USWX - USA Waste Services
 * UTAH - Utah Railway
 * UTAX - Utah Transit Authority (formerly assigned to United Transportation, Inc.)
 * UTBX - Union Tank Car Company
 * UTCX - Union Tank Car Company
 * UTLX - Union Tank Car Company
 * UTPX - Union Texas Petroleum Corporation
 * UTR - Union Transportation
 * UTTX - Trailer Train Company