| October 12, 1990
45¢ Multicolored
Tropical Coast
Scott #C127 |
| April 27, 1991
50¢ Multicolored
Harriet Quimby
Scott #C128 |
| May 17, 1991
40¢ Multicolored
William T. Piper
Scott #C129 |
| June 21, 1991
50¢ Multicolored
Antarctic Treaty
Scott #C130 |
| October 12, 1991
50¢ Multicolored
Bering Land Bridge
Scott #C131 |
| 1993
40¢ Multicolored
William T. Piper
Scott #C132 |
| May 12, 1999
48¢ Multicolored
Niagara Falls
Scott #C133 |
| July 30, 1999
40¢ Multicolored
Rio Grande
Scott #C134 |