Although the domain Twitter.com was first registered back in 2000, it wasn't until 2006 that the Twitter we know today was born. Twitter was founded by Evan Williams, Jack Dorsey, Noah Glass, and Biz Stone. The idea for an SMS like service came out of a brainstorming session; it was code named twttr and used the typical five-character length of American SMS short codes. According to Dorsey, they chose to call the service Twitter because "the definition [of the word twitter] was a short burst of inconsequential information and chirps from birds and that's exactly what the product was."
Twitter was introduced to the public on July 15, 2006. Its popularity really started to skyrocket after the 2007 South by Southwest conference where they saw Twitter usage increase from 20,000 tweets per day to 60,000. Then on January 15, 2009, Flight 1549, piloted by Captain Chesley 'Sully' Sullenberger, went down in the Hudson River. Janis Krums, who was nearby on a ferry when the plane went down, tweeted, "There's a plane in the Hudson. I'm on the ferry going to pick up the people. Crazy," along with a now-famous photo of the plane in the water. Thirty minutes later Krums was interviewed on live TV. According to Dorsey, "Suddenly the world turned its attention because we were the source of news - and it wasn't us, it was this person in the boat using the service, which is even more amazing."
Today, Twitter sees 500 million tweets per day from 230 million active monthly users according to its website and it looks like it won't be slowing down any time soon. After it's recent IPO, the company saw its shares jump 73% in its market debut on November 7, 2013, valuing the company at a little over $31 billion.