To determine which event should appear first on a timeline, we can look at the dates of each event:
- The formation of the state of Israel - May 14, 1948
- The Iran hostage crisis - November 4, 1979
- The Persian Gulf War - August 2, 1990 (start)
- The 9/11 attack on the World Trade Center - September 11, 2001
Based on these dates, the first event to appear on the timeline is the formation of the state of Israel.