SG-18
From The Stargate Omnipedia
One of the many units deployed out of Stargate Command inside Cheyenne Mountain.
KEY EPISODES
Death Knell - General Hammond mentions SG-21, confirming that the SG-18 unit must have been formed by 2004.
200 - MSgt. Harriman mentions that SG-18 is among those waiting on P2C-106 to celebrate Colonel Mitchell's two-hundredth trip through the Stargate.