While cities in Island and Snohomish counties established their own libraries in the early 20th century, the first inter-city system was created by voters in unincorporated Snohomish County in 1944. The system's creation was spurred by the state legislature's approval of rural library districts in 1941. The new Snohomish County Library was temporarily headquartered in the basement of the separate Everett Public Library before moving to another building in Everett. The system's first library was in Alderwood Manor; the first bookmobile was purchased in 1947.
The new library system was named "Sno-Isle" to reflect the two counties. A new headquarters building near Marysville was constructed in 1965. Initially, the Sno-Isle Regional Library signed contracts with incorporated cities to operate their libraries and join the system for a fixed amount. Rural branches would rely on property taxes generated within the district, as well as donations from organizations and members of the community. The library system purchased and installed its first computerized catalog system in 1983. Incorporated cities began voting to annex themselves into the Sno-Isle district in the late 1980s, with promises of new libraries and potential cost savings over the contracted service.
A major levy lift of 9 cents per $1,000 in assessed property value was approved by voters in May 2018 by a margin of less than 0.5 percent. All Sno-Isle branches were closed in March 2020 due to the COVID-19 pandemic, but reopened with curbside pick-up service three months later. In-person services resumed at some branches in early 2021.
As of 2018, the Sno-Isle Libraries system has 23 branches. They serve every city in Island and Snohomish counties, with the exception of two cities: Everett, which has its own system, and Woodway, which had contracted service until 1978. The system covers an area of 2,260 square miles (5,900 km2) and a population of over 700,000 residents.
The Sno-Isle Libraries system is headquartered at an administration and processing center on the Tulalip Indian Reservation, west of Marysville. It is governed by a seven-member board of trustees, of whom two are appointed by Island County and five by Snohomish County. The system is overseen by an executive director that is appointed by the board of trustees. Jonalyn Woolf-Ivory, a longtime library employee, was appointed as executive director in 2002 and retired in 2018.
The library system has annual expenditures of $77 million and revenues of $74 million. As of 2017, 98 percent of revenue was generated by a property tax levied on all properties within the district. The remaining two percent of revenue were sourced from a timber excise tax, a leasehold excise tax, contract fees from municipal governments, and donations.
In 2022, Sno-Isle had a total circulation of 7.4 million items, placing it third in Washington behind the King County Library System and Seattle Public Library. It had the state's fifth-highest turnover rate, at 4.74 checkouts per item.: 22
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Nash, Ashley (January 11, 2024). "Amid deficit, Everett eyes joining fire authority, Sno-Isle libraries". The Everett Herald. Retrieved March 5, 2024. https://www.heraldnet.com/news/amid-deficit-everett-eyes-joining-fire-authority-sno-isle-libraries/
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Bray, Kari (January 2, 2018). "Sno-Isle library to open in Smokey Point, in leased space". The Everett Herald. Retrieved January 5, 2018. https://www.heraldnet.com/news/demonstration-library-set-to-open-in-smokey-point/
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Gates, Sophia (June 5, 2024). "Coming soon: A Sno-Isle library on the ground floor, with housing above". The Everett Herald. Retrieved June 5, 2024. https://www.heraldnet.com/news/coming-soon-a-sno-isle-library-on-the-ground-floor-with-housing-above/
"Library Service Providers Listed by County". Municipal Research and Services Center. Retrieved March 12, 2022. https://mrsc.org/Home/Explore-Topics/Governance/Forms-of-Government-and-Organization/Special-Purpose-Districts-in-Washington/Library-Service-Providers-Listed-by-County.aspx
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Buell, Douglas (December 13, 2017). "Lakewood/Smokey Point Library to celebrate grand opening in January". Marysville Globe. Retrieved January 5, 2018. http://www.marysvilleglobe.com/news/lakewoodsmokey-point-library-to-celebrate-grand-opening-in-january/
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Reardon, Kate (March 25, 2002). "Sno-Isle library hires chief". The Everett Herald. Retrieved January 5, 2018. http://www.heraldnet.com/news/sno-isle-library-hires-chief/
Bray, Kari (May 21, 2018). "Sno-Isle Libraries executive director retiring after 33 years". The Everett Herald. Retrieved February 16, 2019. https://www.heraldnet.com/news/sno-isle-libraries-executive-director-retiring-after-33-years/
"2023 Adopted Budget" (PDF). Sno-Isle Libraries. November 21, 2022. Retrieved March 5, 2024. https://www.sno-isle.org/wp-content/uploads/sites/90/2022/12/2023-Adopted-Budget.pdf
Stevick, Eric (December 1, 2017). "Sno-Isle Libraries will have to make cuts or go to voters". The Everett Herald. Retrieved January 5, 2018. http://www.heraldnet.com/news/sno-isle-libraries-will-have-to-make-cuts-or-go-to-voters/
"Funding sources". Sno-Isle Libraries. Retrieved January 5, 2018. https://www.sno-isle.org/funding/sources
"2022 Washington Public Library Statistical Report" (PDF). Washington State Library. September 2023. pp. 64–66, 70, 74. Retrieved March 5, 2024. https://apps.sos.wa.gov/_assets/library/libraries/libdev/2022stats.pdf
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