Western law enforcement has used the assistance of volunteers since territorial days to track down bandits or to look for lost people. These volunteers were usually formed into a group called a posse. In 1941, Maricopa County in Arizona began formally structuring these volunteers into different posses based upon their expertise. Today the Sheriff’s Office has about 50 different Posse’s of which has a combined membership of over 3,000 volunteers.

One of the earliest organized non-horse posses was the Maricopa County Sheriff's Jeep Posse, formed in 1956. The Jeep Posse carries on the tradition of the early posses and participates in all phases of law enforcement. The "Jeeps" provide valuable assistance to virtually every division within the Sheriff's Office. This assistance includes emergencies of every nature; particularly Search & Rescue missions, maintaining law & order on the lakes and rivers, backing up patrol deputies on dangerous calls; providing traffic control for accidents, special events and other duties as called upon by the Sheriff's Office.

The Jeep Posse's main expertise is in the area of Search & Rescue. Maricopa County comprises 9,226 square miles, which makes it the 9th largest county and the Sheriff's Office the 4th largest in the United States. Much of the county is uninhabited desert and mountain terrain. As a result of the high use of these recreational areas by off-road enthusiasts, hikers, campers and boaters, (most of whom are untrained and unequipped for survival) all have become subjects of Search & Rescue operations. Stranded motorists, downed aircraft, and train derailments have also occurred in these remote areas. In response to this situation, Maricopa County has developed one of the most efficient and successful Search & Rescue organizations in the entire nation.