As mentioned in the explanation:

While the notion that policing forces in the US grew out of slave patrols is widespread, it is not strictly speaking true - in the 1850s, many locales simply did not have formal policing forces, which was still a cutting-edge innovation from Britain (see: Peele's Principles ). In the post-Civil War era, Federal Reconstruction in the South led to an increasing need for abstract law enforcement which did not rely on mob consensus.