Local Health Department or District. Counties' legislative authorities are charged with establishing either a county health department or a health district to assure the public's health. Local health departments and health districts can take various forms and include a single county health department or district, a combined city and county health department, or several counties can join a health district.

Each local public health jurisdiction is governed by a local board of health (board). 

For counties without a home rule charter, the board is comprised of the board of county commissioners and unelected members from the following three categories that must be approved by a majority vote of the board of county commissioners:

• public health practitioners, employees of health care facilities, and health care providers, which includes medical ethicists; epidemiologists; individuals experienced in environmental public health, such as a registered sanitarian; community health workers; holders of master's degrees or higher in public health or its equivalent; employees of a hospital located in the county; and any of the following providers holding an active or retired license in good standing: physicians or osteopathic physicians, advanced registered nurse practitioners, physician assistants, nurses, dentists, naturopaths, or pharmacists;
• consumers of public health, which includes residents who have self-identified as having faced significant health inequities or as having lived experiences with public health-related programs; and
• other community stakeholders, which consists of persons representing the following types of organizations: active, reserve, or retired armed services members, community-based or nonprofit organizations that work with populations experiencing health inequities in the county; the business community; or the environmental public health regulated community.

If the number of board members selected from these three categories is evenly divisible by three, there must be an equal number of members selected from each of the three categories. If there are one or two members over the nearest multiple of three, those members may be selected from any of the three categories. If the board demonstrates it attempted to recruit members from all three categories and was unable to do so, the board may select members only from the other two categories. There may be no more than one member selected from one type of background or position.

If a federally recognized Indian tribe holds reservation, trust lands, or has usual and accustomed areas within the county, or if a 501(c)(3) organization registered in Washington that serves American Indian and Alaska Native people and provides services within the county, the board must include a tribal representative selected by the American Indian Health Commission. The number of members selected from the three categories and the tribal representative must equal the number of city and county elected officials on the board.

The county may, at its discretion, expand the board to include elected officials from cities and towns and individuals other than elected officials, as long the city and county elected officials do not constitute a majority of the total membership of the board.

County Governance.  The state constitution allows counties to adopt their own form of government by county charter. Non-charter county commissions are comprised of a three-member board elected on a partisan basis to four-year staggered terms. Any non-charter county with a population of 400,000 or more must have a board of commissioners with five members. Any county with a population greater than 300,000 and less than 400,000 may voluntarily increase the number of commissioners from three to five with voter approval.

For counties without a home rule charter where the board of county commissioners is comprised of five commissioners, the board of county commissioners may adopt an ordinance reducing the number of county commissioners that are members of the local board of health, provided the board of health includes at least one county commissioner.