Sound Transit Express (ST Express) is a network of regional express buses, operated by the multi-county transit agency, Sound Transit. The routes connect major regional hubs throughout 53 cities in three counties (King, Pierce, and Snohomish) in the Puget Sound region. Sound Transit Express ranks first in the nation in the number of commuter bus passengers carried and in vehicle miles driven. The first nine routes and 114 buses began carrying passengers on September 20, 1999.