| 1 | WRDX | Ward Tank Car Line | 7/1930-4/1938 | | NAKINA |
| 2 | WRDX | Ward Tank Line | 1/1941 | | NAKINA |
| 3 | WRDX | Ward Tank Line (Mrs. W.J. Ward, owner) | 1/1943 | | NAKINA |
| 4 | WRDX | Wyodak Resources Development Corp. | added 1/1980; 1/1980; eliminated 10/1982 | | NAKINA |
| 5 | WRDX | Iowa-Illinois Gas & Electric Co. | added 10/1982; eliminated 7/1983 | | NAKINA |
| 6 | WRDX | Iowa-Gas & Electric Co. | added 10/1983; 1/1994 | | NAKINA |
| 7 | WRDX | Iowa-Illinois Gas & Electric Co. | eliminated 4/1996 | | NAKINA |
| 8 | WRDX | MidAmerican Energy Co. | added 4/1996; 7/2000-7/2005 | | NAKINA |
| 9 | WRDX | Ward Tank Car Line | Apr-38 | | NRHS |
| 10 | WRDX | Wyodak Resources Development Corp. | added 1/80; 1/80; eliminated 10/82 | | NRHS |
| 11 | WRDX | Iowa-Illinois Gas & Electric Co. | added 10/82 | | NRHS |
| 12 | WRDX | Iowa-Gas & Electric Co. | added 10/83; 1/94 | | NRHS |
| 13 | WRDX | Iowa-Illinois Gas & Electric Co. | eliminated 4/96 | | NRHS |
| 14 | WRDX | MidAmerican Energy Co. | added 4/96; 7/2000 | | NRHS |
| 15 | WRDX | *WARD TANK LINE | | | PWRC |
| 16 | WRDX | *WYODAKE RESOURCES DEVELOPMENT CORP. | | | PWRC |
| 17 | WRDX | +MIDAMERICAN ENERGY COMPANY [IOWA-ILLINOIS GAS & ELECTRIC CO.] | | | PWRC |
| 18 | WRDX | Iowa-Illinois Gas and Electric (MidAmerican Energy) | | | RSRV |
