Its history dates back to the early days of World War II. Soon after the attack on Pearl Harbor, the Harris County Sheriff’s Department organized a group of volunteers known as the "Civil Defense Organization". This group of citizens, some three hundred strong, represented people from various occupations. The organization’s goal became the ability to assist the Sheriff during any disaster. During those early days of the war many members left the Civil Defense Organization to volunteer for U.S. armed forces service overseas.

After the war, Harris County Sheriff Buster Kern recognized the potential of a volunteer organization formed of dedicated citizens. Kern began using Civil Defense Organization members as local law enforcement volunteers. The name of the organization was changed to the "Auxiliary Deputy Sheriff’s Group", which more accurately reflected its revised role in the Sheriff’s Department.

Although a new concept for Harris County, the use of police reserve forces has been a Texas tradition. State law preserved reserve law enforcement organizations over the years and made the reserve deputy an essential part of Texas law enforcement heritage. The concept of a reserve force dates back to the formation of a group of volunteers in the 1820’s to fight Comanche Indians. That first volunteer organization became the Texas Rangers, the nation’s oldest state law enforcement agency.

The Harris County Auxiliary Sheriff’s Group continued to grow and steadily strengthen as a volunteer unit during the 1950’s. During 1957, these volunteers formally organized as the present Harris County Sheriff’s Reserve and became a nonprofit corporation registered with the state.

The 1960’s saw the Reserves expand in numbers to meet the rising need for additional law enforcement. During this period, Grant Ilseng, a Houstonian nationally famous for trap and skeet shotgun shooting, formed the Marine Reserve unit, which included several qualified SCUBA Deputies.

In the early 1970’s, the Reserves reorganized to retain three goals:

• Maintain a close liaison with the regular Sheriff’s Department
• Provide adequate supervision of reserve deputies
• Be able to call out large quantities of trained deputies in a short period of time with a minimum of effort

By the end of 1972, the Reserves numbered approximately 600 dedicated men and women with a common goal to assist the Harris County Sheriff in improving the area’s quality of life. Legislative action in 1972 mandated state training certification laws for reserves as outlined by the Texas Commission on Law Enforcement Officer Standards and Education (TCLEOSE). As a result, the number of reserves dropped while the level of professionalism increased. During 1973, it is estimated that the organization’s 450 reservists combined time equaled more than $1.5 million in savings on an annual basis to the Harris County Sheriff’s Department.