Oregon law allows a person to apply to set aside the record of an arrest and certain convictions. Expungement is the process by which a criminal conviction and/or arrest is destroyed and erased from court records. The court orders official records sealed and it is as if the violation leading to the arrest or conviction did not occur. Some crimes may not be expunged. The Oregon Statute outlining this process is ORS 137.225.
The website for Washington County Circuit Court has additional information and forms.