What's the difference between a police officer
and a sheriff's deputy?
"What mayor wouldn't prefer having a police
chief appointed by that mayor and serving at
that mayor's pleasure versus a sheriff elected
in his or her own right?" ~ Barry M. Baker
As a police officer anywhere in the country, your law
enforcement duties will be uniform and wide
ranging; whereas, the duties of sheriffs' deputies
may be limited as to law enforcement activities...or
their duties may be identical to yours.  For instance,
you might be a police officer with a county police
force where sheriffs' deputies in your county are
responsible only for the security of court houses,
prisoner transport, and other general business of
the court.  Then, in the county bordering your
jurisdiction, that county has no police department,
and its sheriffs' deputies are responsible for all law
enforcement activities to include patrol and criminal

Nearly all densely populated cities and counties will
have their own police departments.  As the
population thins out, you'll see more smaller
agencies such as borough and township police
departments.  You might be in a small township
department where you're supported by state police
or sheriffs' deputies.  In this scenario, the law
enforcement mission and duties of all are identical.

The way sheriffs' deputies differ in their law
enforcement missions from police officers is really all
about politics.  What mayor wouldn't prefer having
a police chief appointed by that mayor and serving
at that mayor's pleasure versus a sheriff elected in
his or her own right.  While the mayor will have total
control over the chief, the sheriff, God forbid, could
be of the opposite political party.  When an elected
sheriff has the responsibility for all law enforcement
duties within a jurisdiction, that sheriff becomes a
very powerful and politically influential sheriff.

I've linked you below to a history of the Las Vegas
Metropolitan Police Department.  This is an example
of a law enforcement agency labeled as a police
department and headed by an elected sheriff.
"On July 1, 1973 the Clark County Sheriff's Office
and Las Vegas Police Department were deactivated,
and the Las Vegas Metropolitan Police Department
became the official police force for Las Vegas and
the unincorporated areas of Clark County.  Sheriff
Ralph Lamb took over as the LVMPD head, with
John Moran, former LVPD Police Chief, as the
Police and
Copyright © 2019  Barry M. Baker  
Let's start from the beginning.  The sheriffs have
been the chief law enforcement officers throughout
the United States since the 17th Century and long
before the formation of professional police
departments.  Today, the Sheriff continues to be
the top law enforcement officer in most jurisdictions.

Theoretically, the Sheriff could take over an
investigation from a police department if he or she
wished since the Sheriff is an elected official in
contrast to a police chief, police commissioner or
superintendent who are appointed to their positions
by mayors, city managers, or governors.  I say
theoretically, because you won't see sheriffs
interfering with police departments.