A knowledgeable Gamasutra reader has pointed out that the "Old Barn" which has reportedly been destroyed was only the home of the The Sierra Network; Sierra Online itself was headquartered in a separate building. The original story has been updated accordingly.
The former Sierra Network headquarters in Oakhurst, CA is believed to have been one of the structures burned to the ground today by a wildfire that broke out near the town.
Long-running Sierra Online fansite Sierra Chest
caught the news, and reports that former Sierra Online employees who still live in the area have confirmed the facility's destruction.
The building, once fondly known as Sierra Online's "Old Barn," was the birthplace of the Sierra Network (later renamed the ImagiNation Network), launched to the public in 1991 as one of the very first graphical online multiplayer worlds.
It is unclear what the building was being used for at the time of the fire, or what may have been destroyed in the blaze.
In an unfortunate coincidence, Activision Blizzard recently announced plans to revive the Sierra brand as an indie publishing label
and put out a new Odd Gentlemen-developed King's Quest
game in 2015.