Oregon Revised Statutes Elections § 246.410

(1)(a) After each federal decennial census, the Secretary of State shall prepare detailed and comprehensive directives providing guidelines for fixing precinct and other electoral district boundaries based on census population figures.

(b) After the federal decennial census and before the Legislative Assembly or Secretary of State, whichever is applicable, apportions the state into congressional and legislative districts, the secretary shall deliver the directives to:

(2)(a) In accordance with any directive distributed by the Secretary of State under this section, the county clerk, not later than the 30th day before an election, may create, combine or divide one or more precincts. The number of electors to be included in a precinct shall not exceed 10,000. The county clerk shall fix the boundaries of the precincts and designate the precincts by numbers or names.

(b) A local government or special government body that fixes electoral district boundaries based on census population figures shall fix the electoral district boundaries in accordance with any directive distributed by the Secretary of State under this section.