1981 ... Shuttle launch number one- Columbia

I don't like to rank "most" but these are three events that I have sharp memories of where I was, how I heard, and what I was doing.

1. Terrorist attacks of September 11, 2001. I was 29.

2. Fall of Berlin Wall, November 1989. I was 17 (first semester of college)

3. Launch of Space Shuttle Columbia, April 1981. I was 9 and watched it outside with my school (we could only see the vapor trails)