The oldest law enforcement agency in United States history is the U.S. Marshals Service. President George Washington signed the law that brought this group into existence on September 24, 1789.
US Marshals History
The Judiciary Act gave the Marshals Service the ability to act on all warrants. The Marshals Service creation filled many different roles for law enforcement.
The federal government had reach with them in place, allowing them to act in multiple jurisdictions. It also gave them a direct line to the president's office and vice versa.
When the Marshals were first put in place, every district had one with a four-year term limit. The Marshals had jurisdiction over the local law enforcement and were able to bring on deputies to help them.
The Marshals employed locals most of the time, either swearing them in on a case-by-case basis or working with them long-term. Many of the first Marshals had a military background and fought in the Revolutionary War. The district of New Yorks's first Marshals were Congressman Thomas Morris and Wiliam Stephens Smith, John Adam's son-in-law.
While movies show Marshals in the old west hunting down the bad guys, that wasn't always their job, though it happened occasionally. The Marshals' day-to-day was a little more mundane.
Their responsibilities included serving subpoenas and warrants and delivering paperwork. They also needed to pay jail space, court fees, attorneys, and clerks of the court.
Marshals also had to ensure that the court process went smoothly and all witnesses and criminals were present and accounted for when trials began. Oddly enough, they were also responsible for taking the census. This task remained the job of the Marshals until 1870.
As they traveled for the census, they would also provide residents with the latest announcements from the presidents, government officials, and other pertinent information.
The Marshals would report back to local judges, which was also how they would get paid for their completed work. Near the end of the 1800s, they moved to a salaried system.
The USMS reports to the Attorney General today and is a part of the U.S. Department of Justice. Some of their tasks are protecting commercial flights, guarding high-value witnesses, refugees, athletes, and securing areas during riots and protests.