In the North, rich merchants socialized the costs of the guards they hired to protect their assets in port cities through municipalization. In the South, that wasn't the case, and the police are direct descendants from slave patrols.
From Time's "How the U.S. Got Its Police Force"[1]:
> The first publicly funded, organized police force with officers on duty full-time was created in Boston in 1838. Boston was a large shipping commercial center, and businesses had been hiring people to protect their property and safeguard the transport of goods from the port of Boston to other places, says Potter. These merchants came up with a way to save money by transferring to the cost of maintaining a police force to citizens by arguing that it was for the “collective good.”
> In the South, however, the economics that drove the creation of police forces were centered not on the protection of shipping interests but on the preservation of the slavery system.
With regard to police originating from strike breakers, that's also true.
> For example, businessmen in the late 19th century had both connections to politicians and an image of the kinds of people most likely to go on strike and disrupt their workforce. So it’s no coincidence that by the late 1880s, all major U.S. cities had police forces. Fears of labor-union organizers and of large waves of Catholic, Irish, Italian, German, and Eastern European immigrants, who looked and acted differently from the people who had dominated cities before, drove the call for the preservation of law and order, or at least the version of it promoted by dominant interests.
[1] https://time.com/4779112/police-history-origins/