Development began sometime prior to 2002 under the codenames "Grid" and "Gazelle". It was first revealed on March 22, 2002 at the Game Developers Conference purely as a distribution network.
The beta client version was released in 2002 for users of the CS 1.6 beta. It was mandatory to install and use the program for 1.6 beta users, although Steam was still optional. In 2004, WON was shut down and replaced by Steam.
When the release first opened to the public, users found the software to be buggy, chokes in connections to Steam servers, and inability to install the software.
In 2004, Half-Life 2 was released, requiring Steam activation to play.
On 12 September 2007, Valve released the Steam Community. It is a social networking service connecting players to each other.
On 26 April 2010, Valve released a major UI update to Steam. It is the largest update since the launch in 2003.