7 oldest (still active) domains

1. symbolics.com - 15-Mar-1985
2. bbn.com - 24-Apr-1985
3. think.com - 24-May-1985
4. mcc.com - 11-Jul-1985
5. dec.com - 30-Sep-1985
6. northrop.com - 07-Nov-1985
7. xerox.com - 09-Jan-1986