Wash. Rev. Code § 27.12.190
The management and control of a library shall be vested in a board of either five or seven trustees as hereinafter in this section provided. In cities and towns five trustees shall be appointed by the mayor with the consent of the legislative body. In counties, rural county library districts, and island library districts, except as provided in RCW 27.12.192, five trustees shall be appointed by the board of county commissioners. In a regional library district a board of either five or seven trustees shall be appointed by the joint action of the legislative bodies concerned. In intercounty rural library districts a board of either five or seven trustees shall be appointed by the joint action of the boards of county commissioners of each of the counties included in a district. The first appointments for boards comprised of but five trustees shall be for terms of one, two, three, four, and five years respectively, and thereafter a trustee shall be appointed annually to serve for five years. The first appointments for boards comprised of seven trustees shall be for terms of one, two, three, four, five, six, and seven years respectively, and thereafter a trustee shall be appointed annually to serve for seven years. No person shall be appointed to any board of trustees for more than two consecutive terms. Vacancies shall be filled for unexpired terms as soon as possible in the manner in which members of the board are regularly chosen.
A library trustee shall not receive a salary or other compensation for services as trustee, but necessary expenses actually incurred shall be paid from the library funds.
A library trustee in the case of a city or town may be removed only by vote of the legislative body. A trustee of a county library, a rural county library district library, or an island library district library may be removed for just cause by the county commissioners after a public hearing upon a written complaint stating the ground for removal, which complaint, with a notice of the time and place of hearing, shall have been served upon the trustee at least fifteen days before the hearing. A trustee of an intercounty rural library district may be removed by the joint action of the board of county commissioners of the counties involved in the same manner as provided herein for the removal of a trustee of a county library.
RCW 27.12.190