Valve the company behind the games such as Half Life and Half Life 2 is located in Bellevue, Washington. They are a exciting and dynamic company well known for picking up mods as retail games and welcoming budding game designers to there head office for tours.
On Jan 15-16, 2014, Valve hosted over 1,200 game developers from around the planet at Steam Dev Devs in Seattle, WA. We've made videos of 28 Steam Dev Days sessions, covering a wide range of game development topics available on the new Steam Dev Days.
SteamWork Development playlist: Youtube.com