Where were you on September 11, 2001? It's a question most people know the answer to—instantly. Across the country, lives were affected by the horrific coordinated terror attacks of the day from New York City to Washington, D.C. and Shanksville, Pennsylvania.
NBC News is asking you to share on Twitter where you were on 9/11 using the hashtag #WhereWereYou911. We're collecting responses from across the U.S. and beyond and posting them.