CopWatch activist Robert West filmed the Columbia County Sheriff's Office (CCSO) inmate transport truck a few years ago. He caught the license plate featured in the screenshot on this page and the video is embedded on this page. The license plate is E258877.
CCSO can be seen taking inmates to the federal courthouse in downtown Portland almost every day. The Columbia County Jail is primarily a federal holding facility. Columbia County is a small county with a contract with the U.S. Marshals, so most of the inmates in Columbia County are being held pursuant to that contract.