This Western Character is a federal law enforcement officer, charged with apprehending fugitives from federal law, protecting the federal courts and ensuring the smooth function of the court system.
The United States Marshals Service was the first federal law enforcement agency created in the young U.S.A., way back in 1789. While its primary duty was to the judicial system, the Service also acted as the local-level representative of federal laws. For example, the Marshals took the census every ten years until 1870.
Marshals have the ability to deputize ordinary citizens (but not military personnel) at need, popularly known as "forming a posse." Since a marshal is directly responsible to the federal government, they're not as likely to be influenced by local politics as The Sheriff or the Town Marshal. That said, many U.S. marshals have also been sheriffs or town marshals before or after their federal service.
Note that the difference between something like the FBI and the US Marshals is that the marshals are expected to go off into the wilderness, usually alone, take into custody and bring back to justice whoever they are sent after. It pretty much requires that you be a total Badass. So while an FBI agent might or might not be a Badass, a US Marshal always is - even if he looks like a nerd. Big duties assigned to the Marshals Service today include Witness Protection and prisoner transport across state lines, as well as the Air Marshals who fly undercover and armed on commercial flights as a counter to hijackings.
Game and Story Use
- If a community in The Wild West has a US Marshal and Sheriff or Town Marshal, they'll probably find themselves at odds from time to time. The former is likely to avoid (or flaunt) local politics in favor of keeping his Federal bosses happy, while the later two must answer locally. See Town Marshal for an explanation of the difference.