| 1 | IESX | Alliant Energy | added 4/2000; 7/2000-7/2005 | | NAKINA |
| 2 | IESX | IES Utilities, Inc. | added 1/1996; eliminated 4/2000 | | NAKINA |
| 3 | IESX | Iowa Southern Utilities Co. | eliminated 1/1996 | | NAKINA |
| 4 | IESX | IESX Corp. | added 7/1981; eliminated 10/1987 | | NAKINA |
| 5 | IESX | Ivan E. Summa | added 4/1974; 1/1975-1/1980; eliminated 7/1981 | | NAKINA |
| 6 | IESX | Ivan E. Summa | added 4/74; 1/75-1/80; eliminated 7/81 | | NRHS |
| 7 | IESX | IESX Corp. | added 7/81; eliminated 10/87 | | NRHS |
| 8 | IESX | Iowa Southern Utilities Co. | eliminated 1/96 | | NRHS |
| 9 | IESX | IES Utilities, Inc. | added 1/96; eliminated 4/2000 | | NRHS |
| 10 | IESX | Alliant Energy | added 4/2000; 7/2000 | | NRHS |
| 11 | IESX | ALLIANT ENERGY [IES UTIITIES; IOWA SOUTHERN UTILITIES; IESX CORP.; IVAN E. SUMMA] | | | PWRC |
| 12 | IESX | IESX Corporation (Alliant Energy) | | | RSRV |
| 13 | IESX | ALLIANT ENERGY | | | SCAC4 |
