Under the provisional government, taxes were equalized by the county courts, which served as ex officio boards of equalization. These boards remained unchanged until legislation passed in 1854 revised board membership to include the county assessor, county auditor (clerk), and county judge. The board received assessment rolls from the assessor, reviewed them for omissions and errors, and returned the corrected rolls to the assessor.

The provisional government created the first circuit court in 1845. All counties formed one circuit, which was served by a single judge appointed by the legislative assembly. Circuit court jurisdiction was original in all civil suits, all actions for money involving more than $150, and all criminal cases. Circuit courts also had appellate jurisdiction from justice courts.

Although circuit courts were dissolved in 1848 by the Act of Congress which established Oregon Territory, most continued to operate through the spring of 1849. The Oregon Constitution re established circuit courts in 1859. These courts assumed the duties held by US District Courts. Circuit courts were also granted the authority to naturalize residents. Appeals from the circuit courts are heard in the Oregon Supreme Court.

The office of county assessor was created in 1845. It was the assessor's duty to determine the amount of real and personal property owned by county residents; the value of that property; and the amount of county, territorial, and school taxes due. This information was placed on given rolls and transmitted to the county sheriff for collection. Assessors have also been members of the county boards of equalization since 1854.

During the provisional and territorial governments, county courts employed clerks for each of the courts of record. The duty of these clerks was to maintain court records. The office of county clerk was first established in 1846. County clerks served both the county and circuit courts and acted as recorders of conveyances. In 1850, county clerks were authorized to record all land claims except donation land claims, which were recorded by the US Surveyor General from 1850 to 1859.

From 1853 to 1859, county clerks were renamed "county auditors." While this term implies fiscal responsibilities, the duties of county auditors were identical with those of county clerks. The office of county clerk was reestablished by the Oregon Constitution.

The office of county coroner was created in 1847. County coroners performed preliminary investigations of deaths by violence or under suspicious circumstances. Coroners had the authority to order inquests, autopsies, or both.

In 1843, the provisional legislative assembly vested the judges of the provisional supreme court with probate jurisdiction. In 1845, the legislative assembly created district (later county) courts to handle probate matters and to administer county business. When justice courts were established in 1846, they were given the power to act as probate courts and as boards of county commissioners.

The Act of Congress which established Oregon Territory in 1848 designated a 3 member county court as a supervisory board for each county. This court was given jurisdiction over juvenile cases and insane commitments and could appoint county election officials. In 1853, the probate duties of the county court were separated from the administration of county business with the election of a probate judge distinct from the 3 member board of county commissioners.

Oregon Territory's first county school official, the county school commissioner, was elected in 1850 to fulfill requirements of the act which created the common school system. The commissioner received school reports, recorded them, and transmitted copies to the territorial school superintendent. County school commissioners were abolished in 1851 and their duties passed to the county court. In 1855, legislation created the office of county school superintendent. The duties of this office were the same as those of the earlier school commissioner.

From 1843 to 1845, county law enforcement was provided by territorial peace officers. In 1845, the legislature created the office of county sheriff. Sheriffs served as conservators of the peace and ministerial officers of the court. Their law enforcement duties included arresting suspects; executing judgments in criminal cases, including the death sentence; taking custody of prisoners; transferring prisoners to territorial and state penitentiaries; serving civil processes; and executing civil judgments. Sheriffs could appoint deputies, jailers and jail matrons.

County sheriffs also served as ex officio tax collectors. Tax collectors received assessment rolls from the assessor, collected current and delinquent taxes, and gave the revenue to the county treasurer.

Until 1854, all surveying in Oregon was performed either by the territorial surveyor or the US Surveyor General. County surveyors were created in legislation passed in 1854 and again by the Oregon Constitution of 1859. The surveyor surveyed land parcels upon request, apportioned fees for surveys, approved plats of land lying outside the corporate limits of towns and cities, and maintained records of surveys performed.

The provisional government created the office of county treasurer in 1843. Treasurers received taxes collected by county sheriffs; distributed revenue to schools, districts, and county sub units; remitted tax revenues to the territorial treasurer; and received and distributed license fee revenues. County treasurers were also responsible for maintaining accurate records of their financial transactions.

From 1843 until 1853, the duties of district attorneys were performed by the provisional and territorial prosecuting attorneys. In 1853, the legislative assembly established the office of district attorney in each judicial district. District attorneys issued criminal indictments, conducted prosecutions, served as legal counsel to all county officers, and served as defense attorney on behalf of individual counties.

Justices of the peace were first appointed at the Mission Meetings in 1841 and were incorporated into county governments when the provisional government was formed in 1843. Justice courts were given original jurisdiction in civil cases which did not include land disputes or sums exceeding $150. Justice court appeals were made to the circuit courts and to the US District Courts. In 1851, legislation allowed each county election precinct to elect a justice of the peace. The Oregon Constitution did not significantly alter the role of justice courts.

The Act of Congress which established Oregon Territory in 1848 replaced the existing county circuit courts with US District Courts. The territory was divided into three judicial districts and each of the three supreme court justices was assigned to a district. US District Courts were established in every county in each judicial district and the presiding justice rotated through the courts under his jurisdiction.

Territorial legislation passed in 1849 gave US District Courts original jurisdiction in all common law and chancery suits where the demand was greater than $100, in all felony cases, and in misdemeanors punishable by penitentiary sentence. US District Courts had appellate jurisdiction from justice courts, probate courts, and county courts. They were also empowered to issue any writs necessary to fulfill these responsibilities.

US District Courts were replaced in 1859 with county circuit courts under the provisions of the Oregon Constitution.