This definition of the region's boundaries does not align perfectly with the geological boundaries of slate deposits, and is based more on the region of the slate industry and slate production. Geologist Charles H. Behre [de], in a 1926 report, included a much larger geographic definition of the Slate Belt that extended the southern boundary to the Lehigh River north of Catasauqua.[4]
History
19th century
The slate industry in the Slate Belt quickly expanded following the arrival of Robert M. Jones, a Welsh immigrant, in 1848. Jones founded Bangor, Pennsylvania and established several slate quarries. The industry continued to expand throughout the 19th century, reaching its peak production in 1903.[5]
At its 19th century peak, the Slate Belt was the world's largest slate-producing region despite its relatively small geographic size, which is 22 square miles.[6]
20th century
In the years leading up to World War I, Pennsylvania was responsible for more than half of the slate production in the United States, and the vast majority of it came from Northampton County in the Lehigh Valley region of eastern Pennsylvania. More than 40% of national slate production during this period came from Northampton County alone.[7]
The slate industry in the region began declining in the first half of the 20th century. During World War I, many quarry owners closed their quarries to allow workers to contribute to the war effort, especially at nearby Bethlehem Steel in Bethlehem.[8] The increased use of other roofing materials, especially asphalt shingles, resulted in reduced demand for slate. Many quarries also removed all of the easily extractable slate present. A final factor to the industry's decline was the Great Depression, which resulted in greatly reduced home constructions that represented the market for slate roofs. Many quarries in the Slate Belt went out of business during this period.[5]
21st century
Three slate quarries remain active in the Slate Belt: one each in Bangor, Wind Gap, and Pen Argyl.[5] Slate quarries that have been abandoned remain recreational popular for swimming, despite the dangers associated with them. Several people have drowned while swimming in them.[9][10][11]
