Or. Rev. Stat. § 202.210 – Ascertainment, apportionment and assumption of indebtedness

(1) Any new county organized under this chapter shall assume and pay, as provided in this section, a just proportion of the indebtedness of the counties from which it is segregated, based upon the last assessed valuation of the original counties, and in proportion that the valuation within the segregated portion bears to the aggregate valuation of the whole original counties.
(2) In the event of a change in boundaries and the addition of a portion of the territory of one county to another county, the county to which such territory is added shall assume and pay, as provided in this section, a just proportion of the indebtedness of the county from which the territory is segregated based upon the last assessed valuation of the county from which the territory is segregated, in proportion that the valuation within the segregated portion bears to the aggregate valuation of the original county from which the territory is taken.
(3) It shall be the duty of the county courts of both the new county organized under this chapter and the counties from which the new county is segregated, or the county courts of the two counties in which a change of boundaries has been effected, to meet together at the county seat of the new county or at the county seat of the county from which such territory is taken by a change of boundaries, on the third Monday in the sixth month following the date of the proclamation of the Governor, as provided for in ORS 202.060. They shall ascertain, as near as may be, the total outstanding indebtedness of the original counties on the first day of January following the election, and from the total indebtedness shall make the following deductions:
1. (a) The amount of all dues for rents.
2. (b) The reasonable value of all public buildings owned by and remaining within the limits of the original counties.
3. (c) The amount of public funds on hand and belonging to the original counties on the day for which its outstanding indebtedness is ascertained by the joint board of county courts, and not belonging to the special funds mentioned in ORS 202.220.
(4) The amount remaining after such deductions have been made shall, for the purposes and as a basis for the settlement, be the amount which the new county or the county acquiring territory by a change in boundaries, shall pay as a portion of, in the proportions specified. Such joint courts shall ascertain and fix the amount the new county shall assume and pay to the counties from which it is segregated, and the amount the county acquiring the new territory by reason of change in boundaries shall assume and pay to the county from which such territory is segregated.
(5) If by a change in county boundaries, an existing county has been eliminated, the county courts of the counties to which the territory formerly constituting the eliminated county has been added shall meet with the court of the eliminated county at the county seat of the eliminated county on the third Monday of the month following the date of the proclamation of the Governor, and shall determine as provided in this section the amount of any net outstanding indebtedness of the eliminated county. Each county to which territory from the eliminated county has been added shall assume and pay its proportional part of the indebtedness of the eliminated county to the county to which the largest area of the eliminated county has been added and such county shall pay off all outstanding indebtedness of the county eliminated. However, the territory of the county eliminated shall be responsible for its own net indebtedness at the time of elimination of the county and the property therein shall be subject to such further tax levies from year to year as may be necessary to retire the outstanding indebtedness of the eliminated county as the same shall come due, but such territory shall not become liable for any outstanding indebtedness of any county to which a portion or all of the eliminated county shall have been added.