Oregon Revised Statutes Cities § 222.610

Any city may surrender its charter and be merged into an adjoining city in the same or another county. Cities having a river as a common boundary, or cities the boundaries of which at the nearest point of proximity are separated a distance of not more than 1,500 feet, for the purpose of ORS 222.610 to 222.710, shall be deemed to be adjoining. No cities may become merged unless a majority of the electors of the two cities affected authorize the surrender and merger as provided in ORS 222.620 to 222.680. The elections at which the surrender and merger are authorized in the two cities need not be held simultaneously, but it is sufficient if both are held within a period of one year.