The YouTube we know today which has over a billion user was set up in February of 2005 by three former PayPal employees, Jawed Karim, Steve Chen and Chad Hurley. The trio later sold it to google for US$1.65 billion and the company is now operated as one of Google's subsidiary company.
The first ever video to be uploaded was in April of 2005, and it was a video of one of the founders Jawed Karim talking about Elephants.
YouTube made a compilation of some of the most viewed videos uploaded to commemorate it's anniversary.