a model of the ultimate form of police. Nevertheless, during the next ten years only two other states created constabulary forces, and these were on a smaller scale than that of the Pennsylvania force. The constabulary form of state police was considered a challenge and a threat to those who maintained a belief in the local control of policing. Many states, therefore, took a "wait and see" attitude, content to let Pennsylvania experiment with this new form of law enforcement.
The third period begins during the years 1915 to 1919 and continues throughout the twenties. Stimulated by the perceived success of the Pennsylvania state police, the war, and growing social unrest, many states began to embrace the concept of state-controlled police forces. Beginning in 1915 and continuing through 1923, twenty-seven states created some type of state police force. The model that many states looked to was the Pennsylvania constabulary system. Yet, after ten years of operation, certain negative aspects of this type of state police had appeared, particularly with regard to their use in policing labor disputes and strikes. For these reasons, many states placed restrictions on their forces to eliminate these problems. Also, the emergence and growing popularity of the automobile created a need for motor vehicle regulation. In response, some states began to create highway patrols during this period. Reaching a peak in 1921, state police development dropped off dramatically as only a few states created new forces during the remainder of the 1920s.
Beginning in 1929, the final stage of state police development covers the entire period of the Great Depression. The creation of new forces and the modification of older ones began to escalate, reaching a peak in 1935 when eleven states organized police forces. The basic feature of this period was the emphasis on highway patrols rather than the military- like state constabularies characteristic of the early twenties. Over 80 percent of the forces created during this period were of the highway patrol type, and these generally were restricted to enforcing only traffic laws. By the end of 1941, every state had established some type of state police or highway patrol. 83
The process of state police development in the United States began with a long period of slow and gradual emergence via individual experimentation by a few states, continued with a period of quickened activity which focused on the constabulary model of policing, and ended with a period of redirection during the thirties, with the focus on traffic control.