Allegheny County Law Library (ACLL) is located on the 9th Floor of the City-County Building in downtown Pittsburgh:

414 Grant Street, Room 921, City-County Building
Pittsburgh, PA 15219

To access the 9th floor of the City-County building, use the Grant Street side elevators. For those who need a wheel-chair ramp, it is located on the Ross Street side entrance to the building.  

For more information on how to access ACLL, please watch the following video.