Port districts are a type of special purpose district.  There are 75 port districts in Washington.  Port districts can include harbors and marine transport, but can also include airports, railroads, and other facilities.  Port districts are funded by property taxes, services fees, lease fees, and bonds.  Ports may also receive funding from the federal government and from the state.

Marine cargo generally comes in three forms: containerized—cargo transported by container, bulk—cargo transported unpackaged, like grain or oil, and break bulk—cargo, such as a car or barrels, that is loaded individually, rather than in containers or in bulk.  Most non-bulk cargo is transported by intermodal container.  Such containers can be transferred between different modes of transportation, for example, from ship to rail, without removing the cargo from the container.

Port districts and port development authorities are prohibited from using port funds to purchase fully automated marine container cargo handling equipment until December 31, 2031.  Port development authority means a port public development authority created by a single port district or jointly created by two port districts in accord with state law.  Container cargo handling equipment is fully automated if it is remotely operated or remotely monitored.  Port districts may use funds to purchase human-operated zero, or near zero, emission equipment and the infrastructure to support the equipment.