If I had seen this in a less reputable publication than The Atlantic, I would have dismissed it immediately as some kind of urban legend or outright fabrication:
Wait, what? So what was the purpose of the Fourth Amendment? Did cities and towns really just have private security forces and no cops as we understand them? I can’t wrap my mind around this–and I majored in history in college.
The idea of a standing, publicly-funded, uniformed police force is certainly a modern one. That doesn’t mean that there was no government policing; it was just a task that was undertaken by various bureaucrats and ministers in more of an ad hoc manner. For example, the courts had officers to serve and enforce warrants or subpoenas, but who wouldn’t really be considered police officers in the modern sense.
ETA: But the Civil War is a little to recent to be used as a demarcation. The NYPD was founded in 1845, for example.
In the middle ages, under the feudal system, those “wealthy landowners” mentioned in the OP’s quote were, in effect, the government. We are talking about aristocrats, dukes, earls, barons or whatever, who ruled over a certain area, but ultimately deriving their legitimacy from the king. It is very misleading to speak of this as “private” policing, as if we were talking about the private security services used by a modern company or modern landowner to guard their property. It is much closer to having local policing being the responsibility of local government entities rather than the national government, which is, of course, how things are mostly done today. The nature of local government has changed a lot, but the relation of policing to government, really not so very much.
Medieval sheriffs were not hired by private individuals. They were appointed by the king. The idea was that the local noble might rule the land but there was also a sheriff who was there to make sure royal laws were being enforced.
So these sheriffs were the early foundations of our modern police departments. They were established by the government (in this case the monarch) and given the job of enforcing the laws on a local level.
Today we think of the Fourth Amendment as mainly applicable to criminal law. However, the original drive behind it was a fear of the seizure power of tax collectors:
There have always been officials empowered to enact the law, but professional police forces in modern times date from the early Industrial Revolution, when cities increased in size to a point where a more formal system was required. Sir Robert Peel more or less invented the modern police force.
Of course, before we had policemen, we had Constables. This title goes back to Roman times when it was more to do with horses, but in medieval times it was a title for the head of the army; however, the term was also used at the local level within the feudal system, describing an officer appointed to keep order.
So the Parish Constable in the middle ages was not far removed from the American Sheriff in the 19th century: He (probably always he) was appointed locally and any costs were paid from local funds. His duties were wide and varied, and included The administration of justice; apprehending offenders and taking them before the magistrates. Acting as the Coroner’s Officer; supervising beggars, vagrants and others in distress passing through the parish and collecting taxes.