While people and dogs have worked together for thousands of years, it's hard to identify the first use of dogs as police "K-9" units, as the practice emerged well before the term came into general use. What seems indisputable is where the story of dogs as crime fighters begins -- in Ghent, Belgium.

From Ghent to NYC

To expand its police force without spending money on more officers, the city of Ghent started using dogs in 1899. Ghent's success spawned similar programs across Europe. In October 1907, New York Police Department Lt. George R. Wakefield traveled to Ghent for training and returned with five dogs. At midnight on Jan. 27, 1908, the department's first canine unit, called Patrol Squad 1, NYPD, hit the streets.

Maryland or Massachusetts?

The NYPD ended dog units in 1951 when the last kennel at Flatbush closed. According to the Law Enforcement Management Institute of Texas at Sam Houston State University, no U.S. police departments used dogs from 1951 to 1954. K-9 units re-emerged in Massachusetts by 1955, but details are sketchy. The Baltimore City Police department website says that from 1914 to 1916 it had access to two, privately owned Airedale terriers who had come from London to live with their U.S. owners. By 1956, the Baltimore police department established its own, in-house unit.

Beyond the Beat

At first, dogs were used to track and tackle suspects or to explore tight, dark spaces. In 1907, the New York dogs were trained to respect police uniforms so they would respond to commands from any uniformed officer. Today, highly trained, sophisticated police or military K-9 dogs can handle these traditional tasks and much more. They are trained to identify drugs, bombs and vapors emitted by explosives using their keen sense of smell. The School of Veterinary Medicine at Auburn University in Alabama offers a program of study called Canine Performance Sciences, where students train vapor sniffing dogs.

Patrol Dog Dox

Historical stories often surface in children's nonfiction books, such as the story of the Italian police dog Dox, called "Il Gigante" (the Giant) by criminals. Dox's story illustrates the intelligence and tenacity that police dogs exhibit on the job. During his 15-year tenure, Dox found lost children and tracked hundreds of criminals. Shot seven times, he recovered from each bullet wound to work another day. According to a surviving picture of Dox, he retired and traveled to Hollywood to start a TV film career. From there, Dox's trail goes cold.