In most counties in Washington, boards of commissioners act as the legislative and chief administrative authority for the county.  These boards must have at least three members, with counties that have more than 300,000 people allowed to increase the number of commissioners to five.  In the seven counties that have adopted a home rule charter, county councils exercise the legislative authority within the county.

However denominated, the legislative authority of each county is required to hold regular meetings at the county seat to transact county business.  The county seat is the primary location of county government, and various other offices and functions required to be located in the county seat.  A regular meeting is a reoccurring meeting that is held in accordance with a schedule set out in an ordinance, resolution, bylaw, or rule.  The legislative authority may hold a joint regular meeting with another county legislative authority at either of the county seats when the agenda is of mutual interest to both counties.

County legislative authorities are also allowed to hold a regular meeting outside of the county seat at another location within the county when the legislative authority determines that doing so will support greater citizen engagement with county government.  This can occur no more than four times a year, and notice of the meeting must be provided at least 30 days prior to the meeting on the county's website, in a newspaper of general circulation, and by email to any county resident who has asked to receive notice.

If a county legislative authority determines that holding a meeting at an alternative location will support greater citizen engagement with county government, then the legislative authority may, with notice, hold up to one regular meeting per calendar month in a city within the county that has a greater population than the county seat, and up to one regular meeting per quarter at another location within the county.  Only one total meeting per calendar month may be held at an alternative location.