Sheriff is an elected position, for a county.  He then has "deputies" who carry out the actual police activities.  More often than not, the sheriff comes from a law enforcement background, though not always.  Some are more experienced than others.  When I lived in Springfield, IL, we had an election for the Sangamon County Sheriff, with the two candidates consisting of a captain, from the Illinois State Police, and a Springfield police officer, who appeared in the Crime Stoppers public service announcements, on tv.  The captain had way more experience in a leadership position, while the "Crime Stoppers Guy," had more public recognition.  Guess which one got elected?

It varies some, in other states.  When I was going to school in Georgia, we had to stand security watch on the school grounds (Navy school) and had a briefing from the local police liason, since we would call in police for any criminal activities occurring on the grounds (it was an open campus, with no security perimeter fence).  There were 5 different police departments with overlapping jurisdiction.  There was the City of Athens police department, the County police, the County Sheriff's police (different agency...never did understand that one), the Georgia State Patrol and the University of Georgia police, who had jurisdiction within 250 yards of any property of the University (which meant a large area of Athens).

State Police tend to patrol state highways and interstates, protect the state government, investigate crimes that occur across county lines and investigate corruption within the state (including corrupt local police and government officials).  I live in Illinois, which has a reputation for political corruption (we send a lot of ex-governors to prison).  County police patrol the county areas, especially smaller communities that don't have their own police force.  I grew up in a little farm town, in Central Illinois, 20 miles from the nearest city.  the Macon County Police would patrol through the town and respond to calls for police assistance and crimes.  We had a town constable, but I believe it was a town council appointment and had no jail or force.

A lot of the United States is still pretty rural and the county agencies (and state police) help police those areas, especially with things like meth trafficking.  We've had issues in our area with ammonia tanks being tapped into by meth manufacturers.  Ammonia is used with farm chemicals and often stored at local farm service bureaus, which are out in the country.

The regulation of the Federal controls on Alcohol, Tobacco and Firearms falls under the Department of the Treasury, since they levy the Federal taxes on those products.  They set up the Bureau of Alcohol, Tobacco and Firearms (the ATF) to enforce those laws.  The Federal Bureau of Investigations is under the Department of Justice and is tasked with enforcing and investigating Federal crimes, like kidnapping, money laundering, organized crime and such.  They also handled counter-intelligence, until 9/11 changed some of the security structure.  Under Hoover, they were the US counter-intelligence and also jockeyed with Army and navy Intelligence for the gathering of foreign intelligence, until the Central Intelligence Agency was formed, after WW2.  The wartime Office of Strategic Services was more focused on strategic intelligence, related to the war effort, sabotage, and coordinating guerrilla activity (modeled after the Special operations Executive, in the UK).  Army and Navy Intelligence focus more on collecting military specific information, in conjunction with the CIA.

Again, there are jurisdictional squabbles.  An ATF case might overlap with the FBI.  If the agents-in-charge are good professionals, they will work together and pool resources; but, there are numerous instances of people not cooperating because someone is butt-hurt about who gets credit.

The FBI also handles cyber-crimes and I have a third cousin who works for that department.

The Drug Enforcement Agency was created to specifically enforce the narcotics laws and investigate drug trafficking, across state lines.

Commissioner is usually a political appointment, while the Chief of Police is usually the administrative head of the police force.  They are usually appointed to the job, but, it doesn't have a term limit, in most municipalities.  The Commissioner might be in charge of emergency services and not just police.  Elliott Ness, of the famed "Untouchables," was Director of Public Safety, in Cleveland, OH, during the Depression, when they had a serial killer operating (The Torso Killer, dramatized in the comic Torso, by Marc Andreyko and Brian Michael Bendis).  he was in charge of police and fire departments.  Again, it varies from city to city.

When crimes cross jurisdictions, you pull in the police force covering the wider area.  If crimes go across municipalities, the county or even state police become involved.  When it crosses state borders, the Federal agencies become involved.

You have to remember that the US Constitution gives specific powers to the Federal government; but, everything else resides within the states.  The end result was a compromise between the early backers of a strong central government and those that wanted autonomy for the individual states.  That has been a battle that has continued and was central to the American Civil War.

It varies from character to character, actor to actor.  It's clear that Kyle MacLachlin and Sherilyn Fenn are being quirky for character reasons so the acting makes sense.  On the other hand, Eric DaRe as Leo Johnson and Dana Ashbrook as Bobby Briggs, just aren't very good actors at all.  

The Department of the Treasury also administers the minting of currency and is in charge of the US Secret Service.  The Secret Service came into being to investigate counterfeiting and grew into the role of being a protective service, for the President.  In the 1800s, they actually used Pinkerton detectives to guard the president.  The bulk of the Secret Service agent activities are devoted to counterfeiting investigations and enforcement and other Treasury law enforcement.  The protective service is a smaller branch.  if you ever watch To Live and Die in LA, the main character, played by William Peterson, is a Secret Service agent, trying to take down a master counterfeiter, played by Willem Dafoe.  At one point, he also is seconded for protection duty, when the President makes a local political appearance.

The Department of the Interior is in charge of the US Fish & Wildlife Service, which enforces federal laws relating to hunting and fishing and other criminal activities on Federal lands, like national parks.  That department also has the Bureau of Indian Affairs, Office of Justice Services, known as the BIA Police, which enforce the law on tribal reservations, in conjunction with tribal police forces.

The Justice Department also administers the US Marshals Service, which is the law enforcement arm of the Federal courts.  They arrest and transport wanted fugitives, including escaped prisoners (as seen in The Fugitive and the sequel, US Marshals.  They also administer the Federal Witness Protection Program, with protects witnesses in Federal criminal trials and those that are resettled under new identities, after testifying in criminal cases, especially against organized crime.  In the 1800, Federal marshals often acted as law enforcement in territories, before they won statehood, such as Wyatt Earp.

9/11 changed several agencies that were folded into the Dept of Homeland Security (hate that name....way too fascist-sounding).  Groups like the US Border Patrol and the US Coast Guard.  Originally, the Coast Guard fell under the Dept of Transportation, in peace time, and the Department of the Navy, during war time.  Then, 9/11 happened and they were moved into Homeland Security.  They still fall under the Department of Defense, when so designated by the President or Congress.

It's a mess, to be sure.  If you've ever watched Yes, Minister/Yes, Prime Minister, with Paul Eddington and Nigel Hawthorne, you understand how the administrators of government try to grow their power by administering more areas.  The same happens in US government.

In regards to stuff like the BATF and DEA, you have to look at the political history of the US.  There has long been a battle between societal forces who wanted to enforce temperance and those who wanted to drink whatever they liked.  There were skirmishes about whiskey taxes back in George Washington's administration, at the beginning of the Federal government.  In the late 1800s, there was a big push by temperance groups to pass and enforce "dry laws" (no alcohol can be sold) and "blue laws" (alcohol can only be sold on certain days and for certain hours).  It ultimately resulted in Prohibition, when the US Constitution was amended to prohibit the sale and manufacture of alcohol.  That led to a sharp rise in organized crime, as they provided protection for bootlegging operations; either smuggling in foreign alcohol (from Canada and elsewhere) or illegal breweries.  They also provided protection for "speakeasies," illegal bars and nightclubs.  In Chicago, this led to brutal gang war, with Al Capone at the top of the mob operations, in Chicago.  The Chicago police and government were pretty much in his pocket.  The Treasury Department assigned Elliot Ness to head operations to take down Capone, forming his famous Untouchables group.  Now, its history is largely Hollywood BS; but, they did eventually get Capone on income tax evasion, which put him in jail and similar things were used to get to organized crime figures.  Prohibition was repealed,; but, the Treasury still had to regulate the Federal excise taxes on alcohol products, as well as those on tobacco and the sale of firearms.  The Drug enforcement Administration came into being in 1973, under the Nixon Administration, to centralize enforcement of Federal Narcotics laws.  It's no coincidence that this came about after the drug culture arose alongside the student activist and anti-war movements.  The agency grew in power under the Reagan Administration, in the 80s, with further drug hysteria, particularly with the trafficking of cocaine from Latin America.  The real iron y is that while the DEA was trying to interdict drug flow, the CIA was carrying out drug trafficking operations in support of the Contras, in Nicaragua, and other clandestine operations in Latin America.  there were several media investigations that uncovered CIA links to drugs that were flowing into US cities, in the late 80s and early 90s.  Project Censored listed those investigations as their most censored news stories, in the early 90s.

The FBI has been featured heavily in film and television, because J Edgar Hoover liked to foster the image of clean cut, heroic law enforcement officers, taking down organized crime.  The reality was that the FBI was pretty soft on organized crime and spent more time go after smaller fish, like bank robbers Bonnie & Clyde, babyface Nelson, and John Dillinger (banks are Federally controlled and bank robbery is a Federal crime).  Hoover hated the Warner gangster movies of the 30s and pushed heavily for films about heroic G-Men.  You also got some about T-Men, or Treasury Agents (Secret Service and such).  Of course, they ignored Hoover's more political use of FBI investigations.  

Effram Zimbalist Jr starred in The FBI, in the 60s and there were later FBI series.  The Wild Wild West was a spy series was ostensibly about a pair of US Secret Service agents, but you didn't see them hunting many counterfeiters.  Dick Tracy was a bit of a mix of the FBI and a city detective.

Law enforcement in the Old West was nothing like what you see in movies.  Wyatt Earp was known more for pistol-whipping criminals than gunfights and the Gunfight at the OK Corral was a political squabble, between Republican (the Earps) and Democrat (Sheriff Behan and The Cowboys) factions, in the area.  Hollywood would rather have you believe it was about cattle rustling, murder (though there was plenty of that involved, after) and other corruption.  How heroic the Earps were depended on which side of the political spectrum you were, until Wyatt Earp's memoir was published and early Hollywood took up the story, cranking out the legend, instead of the truth.  Police shows have been similar, perpetuating more fantasy than actual policing.  Of course, than name of the game is action and drama.  Most people would rather watch the police shoot it out with desperate criminals than see Barney Fife issue tickets to Gomer for parking near a fire hydrant.

Currently watching THE OUTER LIMITS, airing on Talking Pictures TV. While some episodes are “monster of the week” (I did expect something akin to THE TWILIGHT ZONE), some have been very chilling. I wonder, did 1963 viewers find this really scary?

Fascinating.

I confess, my expectations of the show were twists, subtlety, etc. My mistake. I shouldn’t have expected it to be akin to THE TWILIGHT ZONE.