KNOW AND TELL: Twitter celebrates 10th birthday

SAN FRANCISCO (KGO) -- Happy birthday, Twitter!

The social media site famous for hashtags and a 140-character "tweet" limit turned 10 years old today, having evolved from what was originally billed as a "microblogging" site into one of the Internet's most influential means of communication.

The world's first tweet, which was sent by co-founder Jack Dorsey on March 21, 2006, read "just setting up my twttr."

Event though it's Twitter birthday, the company is thanking everyone for making history, driving change and lifting each other up.

When Capt. Chesley Sullenberger safely landed a disabled US Airways plane with 150 passengers into a frigid Hudson River in January 2009, witnesses tweeted photos of passengers being rescued from the floating plane. At the time, it seemed unthinkable that Twitter didn't exist just a few years earlier.

Now presidents and the Pope even have Twitter accounts.

Twitter is celebrating this milestone at each of its offices around the world, including San Francisco.

The Associated Press contributed to this story.

Every weekday, ABC7 brings you a look at the hottest viral videos. Click here to check out more Know & Tells!