The Seattle Public Library (SPL) is the public library system serving the city of Seattle, Washington. Efforts to start a Seattle library had commenced as early as 1868, with the system eventually being established by the city in 1890. The system currently comprises 27 branches, most of which are named after the neighborhoods in which they are located. The Seattle Public Library also includes Mobile Services and the Central Library, which was designed by Rem Koolhaas and opened in 2004. The Seattle Public Library also founded the Washington Talking Book & Braille Library (WTBBL), which it administered until July 2008.

The King County Library System (KCLS) is a library system serving most 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. Patrons can check out 100 items at once and hold up to 50 items.