Why do some places have just police, just sheriffs, or both?
I know how sheriffs and police officers differ in their duties. What I'm curious about is why some towns/counties have JUST police or JUST sheriffs, while others have both.
For example, the county I live in has both. When I went on vacation to Maine over the summer, the county had just sheriffs; any police officers worked for whatever town hired them. Why is that?