Garrett County is the westernmost county of the U.S. state of Maryland. As of 2000, the population was 29,846. It was named for John Work Garrett (1820-1884), president of the Baltimore and Ohio Railroad from 1858 until his death in 1884. Its county seat is Oakland. Garrett County lies in the Allegheny Mountains, which forms the western portion of the Appalachian Mountains. The western part of the county, drained by the Youghiogheny River, is the only part of Maryland within the Mississippi River watershed.