Allegany County is a county located in the northwestern part of the US state of Maryland. It is part of the Cumberland, MD-WV Metropolitan Statistical Area. As of 2010, the population was 75,087. Its county seat is Cumberland. The name Allegany may come from a local Lenape word, welhik hane or oolikhanna, which means 'best flowing river of the hills' or 'beautiful stream'. A number of counties in the Appalachian region of the US are named Allegany, Allegheny, or Alleghany.
The western part of Maryland (including the present Allegany County) was originally part of Prince George's County when Maryland was formed in 1696. This county included six current counties, and by repeated splitting, new ones were generated: Frederick from Prince George's in 1748; and Montgomery and Washington from Frederick in 1776.
Allegany County was formed in 1789 by the splitting of Washington County. At the time it was the westernmost county in Maryland, but a split in 1872 produced Garrett County, the current westernmost county.
The county has a number of properties on the National Register of Historic Places.