The Multnomah County Sheriff's Office was established in February 1854, with William L. McMillen as the first
sheriff; he served until 1862. In the past, as recently as the 1980s, the position was essentially the "top cop" in the county, performing law enforcement for the bulk of the county's population. , however, as the unincorporated areas of the county have diminished, 85% of sheriff's office employees work in corrections rather than law enforcement. On July 1, 2015, the Sheriff's Office began policing services for the city of Troutdale. In a 10-year agreement, the officers and civilian personnel of the Troutdale Police department were brought in as sworn deputies and employees of the Sheriff's Office. The agreement was reported to save the City of Troutdale over $900,000 per year over a ten-year period. The deal also included leasing of the Troutdale Police Community Center. The Law Enforcement patrol, property, and records divisions were also moved from the Hansen Building to this location in July, 2015. The sheriff's office oversees a budget of $118 million. In 2023,
Nicole Morrisey O'Donnell became the first female Sheriff in the agency's history. Overdoses among inmate escalated due to illegally smuggled drugs by inmates. In August 2023, a strip search was put back into place in response. In January 2025, MCSO updated their vehicle livery. == Controversies ==