This is not accurate.
The timeframe is not wrong; it is true that the concept of the modern police, at least in the US, was largely based on the Peelian model created in London in the 1820s. But saying it evolved from "warehouse guards and slave patrols" is ahistorical. Most modern police forces modeled after London's Metropolitan Police replaced night watch systems that have been around for literally all of recorded history.
There are some pretty big differences between the UK policing model and the one used in the US.
The UK model was set up against the backdrop of the Napoleonic Wars (the French police's role included monitoring dissent, suppressing political opposition [1] and even censoring books) and the Peterloo Massacre [2] (where cavalry were set on a peaceful protest campaigning for more than 2% of people to be allowed to vote)
The Peelian model [3] is one of 'policing by consent' where the police focus their efforts on the sorts of crimes the average citizen wants solved - rather than on suppressing political dissent, or censoring books, or launching cavalry charges against protests. Peel's police aren't a military force, which is why very few of them have guns.
If the American police are based on Peelian principles, then an awful lot of the principles have gotten lost in translation.
[1] https://en.wikipedia.org/wiki/Joseph_Fouch%C3%A9#In_Napoleon... [2] https://en.wikipedia.org/wiki/Peterloo_Massacre [3] https://en.wikipedia.org/wiki/Peelian_principles#The_nine_pr...