The Seattle Worldcon Organizing Committee was founded in 1990, to bring together disparate groups within Seattle fandom to work together on a Westercon bid, and to provide a separate corporate umbrella for the Westercon to protect other groups from any liability or deficit that might arise. Since then, it has organized the following conventions and bids:

Seattle in 2011 Worldcon bid (starting 2006)
Chairman: Bobbie DuFault
For the 50th anniversary of Seacon, the 1961 Seattle Worldcon, SWOC bid to bring the Worldcon back to Seattle. The bid was announced at LACon IV in 2006.

ConComCon (starting 1994)
Chairman: Sally Woehrle
Location: Holiday Inn Seattle — Seatac Airport
ConComCon is an annual convention for convention organizers held in the Pacific Northwest; in recent years it has been in Seattle, Portland, and Cle Elum.

Cascadia Con (2005)
Chairman: Bobbie DuFault; Vice Chairs: Pat Porter, Susan Robinson
Location: Seatac Airport Hilton and Conference Centre
Cascadia Con was the 8th North American Science Fiction Convention (or "NASFiC") held under the auspices of the World Science Fiction Society.

Westercon 56 (2003)
Chairman: William Sadorus
Location: Seatac Doubletree

In 1996, SWOC launched a bid (charied by Pat Porter) to bring the Worldcon to Seattle in 2002. (See Seattle in 2002.) The bid was terminated in 1999 when it lost its facilities. The 2002 Worldcon, ConJose, was held in San Jose.

Westercon 50 (1997)
Chairman: Sally Woehrle
Location: Seattle Sheraton

Westercon 46 (1993)
Chairman: Richard Wright
Location: Bellevue Red Lion

Past SWOC Chairmen
2000 Marjorie Rosen
2001-2002 Sally Woehrle
2003 Shawn Marier
2004 Sally Woehrle
2005 Shawn Marier
2006-2007 Jerry Gieseke

Taken from a Westercon 50 page.