Did you know that on this date (June 14) in 1777, the Continental Congress adopted the flag that was sewed by Betsy Ross, called the Stars & Stripes?
The holiday was officially proclaimed by Woodrow Wilson in 1916 and has now been celebrated for nearly a century and a quote by Wilson was selected as the Thought for Today by the AP and published on the Washington Post's website: "The flag is the embodiment not of sentiment, but of history."

{1917 Flag Day poster found via Wikimedia Commons, owned by Library of Congress}
If you're a fan of history and would like to learn more about Flag Day, check out this piece by Scott Allison and George Goethals on their "Heroes" blog discussing Betsy Ross' place in history and the questions that surround the origins of the Stars & Stripes.
Also, you could learn more about Flag Day directly from the US Library of Congress - the also offer some pretty cool images of the flag and historical Flag Day celebrations.