The 11-story (185 feet or 56.9 meters high) glass and steel building in the downtown core of Seattle, Washington was opened to the public on May 23, 2004.

Rem Koolhaas and Joshua Prince-Ramus of OMA/LMN were the principal architects, and Magnusson Klemencic Associates was the structural engineer with Arup.

Arup also provided mechanical, electrical, and plumbing engineering, as well as fire/life safety, security, IT and communications, and audio visual consulting.

The library has a unique, striking appearance, consisting of several discrete "floating platforms" seemingly wrapped in a large steel net around glass skin.

That library, at 55,000 square feet (5,100 m2), with an extension built in 1946, eventually became too small and cramped for the city's growing population by the 1950s; it had also sustained structural damage from the 1949 Olympia earthquake.

A remodeling finished in 1972 gave the public access to the fourth story, dedicated to the arts and sound recordings.

By the late 1990s, the library became too cramped again and two-thirds of its materials were held in storage areas inaccessible to patrons.

Renewed consciousness of regional earthquake dangers drew concern from public officials about the seismic risks inherent to the building's design.

Ramus, formerly a Seattle resident, found out from his mother one day in advance that the library board was inviting interested firms to attend a mandatory public meeting.

The collection occupies the sixth, seventh, eighth, and ninth stories on a continuous series of shelves with a maximum slope of 2 degrees.

[23] New functions include automatic book sorting and conveyance, self-checkout for patrons, pervasive wireless communications among the library staff, and over 400 public computer terminals.

[28] Lawrence Cheek, the architecture critic for the Seattle Post-Intelligencer, revisited the building in 2007 and found it "confusing, impersonal, uncomfortable, oppressive" on the whole, with various features "decidedly unpleasant," "relentlessly monotonous," "badly designed and cheesily detailed," "profoundly dreary and depressing," and "cheaply finished or dysfunctional," concluding that his earlier praise for the building was a "mistake.

[31] Researchers examined it as a model case for investigating the interplay between the building's complexity and individual differences in wayfinding ability.