The State Constitution has been amended 83 times since its inception. Article XXIII, Section 1 addresses the process of amending the Constitution and Section 2 deals with constitutional conventions.
Amendments may be proposed in either branch of the legislature. The Legislature must approve the original proposal or an alternative to the proposed initiative with a 2/3 vote. The approved proposal is then placed on the ballot at the next state general election, and becomes law if approved by a majority of the electors. The state constitution may not be amended by voter initiative.
An Index of Initiative and Referenda (1914-date) is available on the Washington Secretary of State’s website. Voters' pamphlets from elections also contain summaries of proposed constitutional amendments.