The City of Walnut's primary public safety services are provided by the County of Los Angeles. The Walnut/Diamond Bar Sheriff's Station keeps watch over 45.2 miles encompassing the contract cities of Diamond Bar and Walnut, and the unincorporated area of Rowland Heights. The station provides police services, including all patrol, investigative and custodial operations to more than 148,000 residents. Programs serving Walnut include Bike Patrol, Volunteers on Patrol, Neighborhood Watch and Substance Abuse Narcotics Education. The Walnut station opened on October 1, 1987. The Captain of the station is David Halm. The station can be reached at 909-595-2264 ext. 2024.