sound transit was created in 1993 by king, pierce and snohomish counties to build a regional rapid transit system. after an unsuccessful proposal in 1995, the agency's plan for regional light rail, commuter rail, and express bus service, named "sound move", was approved in november 1996. st began operating its express bus service, taking over existing routes from local transit agencies, in september 1999; the first commuter rail line, between tacoma and seattle, started in december of the same year; and the first light rail line, tacoma link (now the orange line), began service in august 2003. light rail service in seattle began in 2009, and is the largest part of the sound transit system in terms of ridership. union station in seattle has served as the agency's headquarters since its renovation in 1999.