Fanning's Illustrated Gazetteer of the United States.... (New York: Phelps, Fanning & Co., 1853), 22.
ALLEGHANY COUNTY, in the southwestern part of Pennsylvania. Watered by Alleghany, Youghiogheny, Monongahela, and Ohio rivers. Length of this county, 32 miles; mean breadth, 18, with an area of 575 square miles. The face of the country is peculiarly diversified by depressed vales, lying within large swelling hills, which are productive to their summits. In the bosom of these hills there exist inexhaustible beds of fine bituminous coal. Excellent lime and building stone also abounds. Courts are held at Pittsburgh. Pop. in 1820,34,921; in 1830, 50,552; in 1840, 81,235; in 1850, 138,300.