The King County Library System (KCLS) is a library system serving the residents of King County, Washington, United States. Headquartered in Issaquah, Washington, KCLS was the busiest library system in the United States as of 2010, circulating 22.4 million items. It consists of 50 libraries, a Traveling Library Center, a mobile TechLab, and the ABC Express children’s library van. KCLS offers a collection of more than 4.1 million items, including books, periodicals, newspapers, audio and videotapes, films, CDs, DVDs and extensive online resources. All KCLS libraries offer free Wi-Fi connections. People can check out 100 items and hold up to 50 items.