During the height of the Baltimore & Ohio Railroad, Garrett served as the junction of its Pittsburgh Division with its Berlin branch.

[8] A view of Garrett appeared in a collection of photographs from along the B&O's lines that was published in book form in 1872 and digitized by the DeGolyer Library, Southern Methodist University.

[9] The Western Maryland Railroad ran in an East to West direction on the Brooklyn side of Garrett.

In 1964, the Chesapeake and Ohio Railway (C&O) and the Baltimore and Ohio Railroad (B&O) jointly filed for permission to acquire control of the Western Maryland Railway with the Interstate Commerce Commission (ICC).

[10] According to the United States Census Bureau, the borough has a total area of 0.7 square miles (1.8 km2), all land.

The Casselman River is believed to be named for the Landgraviate of Hesse-Kassel or Hesse-Cassel in Germany.

An imperial immediacy (German: Reichsfreiheit or Reichsunmittelbarkeit) which was a privileged feudal and political status, a form of statehood, which a city, religious entity or feudal principality of minor lordship could attain within the Holy Roman Empire.

Notable landmarks in Garrett include a 10 MW wind farm, the first large-scale wind facility constructed in the eastern U.S. Media related to Garrett, Pennsylvania at Wikimedia Commons