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Municipal Incorporation

This page provides an overview of the municipal incorporation process in Washington State, including related statutes, court decisions, and examples of incorporation feasibility studies.

New legislation: From July 23, 2023 to June 30, 2028, the restriction prohibiting areas within five air miles of a city of at least 15,000 population from incorporating unless the incorporating area has at least 3,000 inhabitants is lifted. Beginning June 30, 2028, the restriction is restored. See HB 1620.


Under Washington law, an area can incorporate as a city if it has a minimum of 1,500 inhabitants. If within five air miles of the boundaries of a city with a population of 15,000 or more, the area must have a minimum of 3,000 inhabitants.

The basic procedure to incorporate is set out in chapter 35.02 RCW, and it includes a petition requirement, review by a boundary review board or the county legislative body in counties without a board, and an election. If the voters approve the proposed incorporation, a primary election to nominate candidates for city council (and a mayor in mayor-council cities) and then an election to select the city council must be held. The new city must officially incorporate at a date set by the initial city council and within 360 days of the incorporation election.

After just two new incorporations in the 1970s and 1980s, incorporation activity surged in the 1990s, especially in the Puget Sound region. For information about cities that have incorporated since 1970, visit our City and Town Forms of Government topic page.


  • Washington State Const. art. 11, § 10 — Establishes the basic authority for cities and towns to incorporate and for the state legislature to enact laws to govern the process of incorporation.
  • Ch. 35.02 RCW — Contains the basic statutory procedures for incorporation as a city in Washington State. It also establishes the legal authority and power of a city during the "interim period," the period between the election of the initial city council and the official date of incorporation. In addition, it addresses issues relating to the continued provision of municipal services after incorporation.
  • Ch. 36.93 RCW — Provides the procedures and guidelines for boundary review board review of incorporations and of other processes, such as annexations, which alter municipal boundaries. Proposed incorporations are "reviewed" by a boundary review board in counties in which boards have been established. According to the Washington State Association of Boundary Review Boards, 15 of the state's 39 counties have boundary review boards.

Examples of Incorporation Feasibility Studies

Miscellaneous Incorporation Documents

Court Decisions

Vashon Island v. Boundary Review Bd., 127 Wn.2d 759 (1995) — The Washington State Supreme Court concluded that there is no constitutionally protected right to have an incorporation petition considered under the law existing at the time a notice of intent to seek incorporation was filed with a boundary review board.

Last Modified: February 28, 2024