A Brief Overview


"In a small way at least, slate was produced in Lehigh and Northampton Counties for well over a century. The first operation recorded was in the hard belt by a company from Baltimore which in 1828 began the Rockdale quarry."


Benjamin L. Miller, Northampton County Pennsylvania Geology & Geography , 1939



An image from an unknown Pennsylvania newspaper showing the "industry's most modern plant" at the Keenan Structural Slate Company of Bangor, Pa. In 1907, this company was the largest manufacturer of genuine Bangor structural, sanitary and marbleized slate. The mills were at the American Bangor and Bangor Excelsior quarries, and their mantel factory was located on North Main Street, in Bangor.

The early history of Pennsylvania's 'Slate Belt' is difficult to pin down. Although viable "commercial slate quarrying" first began in the United States in the Commonwealth of Pennsylvania, specific dates for the earliest quarries in the region are not absolute and the range of influence from these earliest quarries could have been limited. Although some historians offer convincing arguments in favor of specific dates and quarries, many sources contradict each other as is evident in the timeline created for this project.

It is generally accepted that the earliest quarrying in the slate belt district was done in and around the town of Slateford. The General Assembly of the Commonwealth of Pennsylvania granted the first slate quarry charter in the state to James Bell, John Griffiths and Adam Traquair as early as 1805, and a map of Northampton and Lehigh Counties from the Pennsylvania Historical and Museum Commission /Pennsylvania State Archives dated between 1816 and 1821 shows the words "Excelsior Slate quarried" written to the west of the Delaware River just below the Water Gap.

The industry expanded along geological lines extending away from the river. Bangor, the heart of the slate industry for decades, celebrated its Slate Centennial in 1936 suggesting that 1836 was the beginning of the industry in Bangor. The following passages from Nelson Dale's book Slate in the United States is often cited as the most accepted story of the beginning of the industry in the region, setting the date to the 1830's and supporting the 1836 date associated with the Bangor event mentioned above. Some historic evidence, however, contradicts his assessment.

Image Source: Ralph W. Stone (Pennsylvania Geological Survey)

The following is taken from part 2 of Nelson T. Dale's pivotal 1914 book, Slate in the United States.

"In 1831 slate was discovered on Benninger's farm, east of Slatington, and probably near the site of the present Genuine Washington quarries, but extensive quarrying on a commercial scale is not known to have been done here before 1844. In that year, according to tradition, the land mentioned was leased by William Roberts and Nelson Labar who became interested in quarrying from seeing slate outcrops while on a walking trip from Easton to Mauch Chunk (now Jim Thorpe). In 1845 the Welshtown tunnel was also opened and the expansion consequent on this and other quarry operations led to the laying out in 1851 of the town of Slatington by the Lehigh Slate Company, then the chief producer."

Dale suggests in his book that no commercial scale slate quarrying was known to have been done in the district until at least 1844. This idea of "commercial scale" viability was related to the fact that early quarries often served only the immediate surrounding communities due to a lack of means to transport their product. The headline for an article in the Easton Centinel of July 7, 1826, however, read "The Ark 'Experiment' - First of its Kind to Pass Easton on the Way to Philadelphia Loaded with Slate". Frequently used by coal companies, in early periods of industrial development in the U.S., an ark was a temporary boat used in the eastern United States for river transport before slack-water canals and railroads made them obsolete. Any attempt to transport slate from Slateford to Philadelphia, a distance of more than 100 miles on the Delaware, should be seen as an attempt at commercial scale quarrying.

While independent slate quarries had existed for decades in the region, the slate industry proper in Northampton County had its humble beginnings with the enterprising Robert M. Jones, an immigrant from north Wales. An experienced slate worker himself, Jones came to America in 1848 in search of an area in which to begin new slate quarries.


The founder of Bangor, Jones' statue was located at the Bangor High School on the hill east of that city, where the masts of the Old Bangor quarry stood. (The statue can still be seen in Founders Park in downtown Bangor).

By 1855 the slate quarry industry, stimulated by Welshmen who were instrumental in persuading experienced slaters from Wales to emigrate to this country, was already thriving and growing by leaps and bounds. In fact as early as 1850, Henry Darwin Rogers, then State Geologist of Pennsylvania, and his associates recognized five quarries in operation at Slatington and two more eastward near the Delaware Water Gap, one of the latter apparently being the Old Jersey quarry, east of Delaware River. Rogers even writes of one quarry as having been opened in 1812, but some argue that this statement is possibly incorrect.

The following is taken from Northampton County Pennsylvania Geology & Geography by Benjamin Leroy Miller

Slate used for chalkboards and writing slates (also known as school slates) was a large product of the slate industry of the Lehigh Valley. The first school slate factory in the district was started by James and Roberts in 1847 on Factory Street in Slatington, which thus became the center of school slate production in the United States. Five years later blackboard making also began, certainly at Slatington and probably at Bangor as well. Sales of roofing slate, however, formed the backbone of the industry.

During the decades between the 1830's and the 1860's , the industry expanded. The Chapman Quarries in the hard vein were developed, the actual charter of that company dated 1864.

By 1880, when state geologist Richard H. Sanders studied the district for the Pennsylvania Geological Survey, slate quarrying was in full swing at all the present centers of production. Indeed in many cases Sanders reported large quarries that had been worked out and abandoned. The arrival, however, of asbestos, paper and tar roofing materials shortly before the peak of slate production in 1903, heralded a general decline in demand for roofing slate. Just prior to this, school slate consumption suffered greatly through displacement by cheap paper notepads and at the hands of the sanitary experts of the public schools. This was accompanied by an intense price competition among the slate men themselves.


"Pennsylvania - This State produces more than half of the entire slate output of the country. The product of 1894 was valued at $1,620,158. Of this amount $1,380,430 is the value of 411,550 squares of roofing slate while the remainder is the value of milled Stock."

Sixteenth Annual Report of the United States Geological Survey to the Secretary of the Interior 1894-95.


Shortly after this productive stretch, a period of marked distress occurred in the industry. Several factors all contributed to the slow and eventual demise of the industry. It was certainly not due to a lack of material available in the ground. Some feel that the depth of the healthy slate for some quarries could have gone down thousands of feet. Labor costs had risen while the availability of men willing to work in the pits had dropped sharply. The Slate Association, which had been created in 1922, appeared before the Senate Immigration Committee to highlight the need for increased immigration to help solve the 300,000 man shortage seen throughout the building industry. Some of the old markets for slate products were on the wane with no possibility of any recuperation; others were being challenged by substitute materials. Freight rates were prohibitive for distance shipments. Added to this, cost accounting was not recognized as furnishing a basis for proper sales prices; expenses were incurred in quarry operations, while prices were being cut in a manner wholly unjustified by the small return on the investment. Then came the greatest of all catastrophes to the industry, the first world war. With the entry of the United States, slate quarrying was almost totally abandoned, being classed as unessential; labor was beyond reach. Immediately after the United States' entry into the war, the organization of the slate industry, so long prevented by internal strife, took place to a considerable degree after more than 75 years. Two large companies, were formed, one to deal with structural products, the other with roofing slate.


Image Source: Joseph Elliott

Slate production in the Lehigh-Northampton district was again able to anticipate better days. General slate production in 1925 had risen over that of any year since 1917. Several quarries, previously abandoned, were reopened.


Although there was general industrial decline in 1921, slate suffered less than other commodities and roofing slate produced in 1928 experienced a sales increase (although artificially inflated) over all previous years. Electrical slate had become an important factor in the development of the industry. The tendency to standardize specifications was noticeable. All in all, despite the severe general depression of 1930- 32, in which the slate industry suffered as much as others, it seems as though slate was gradually regaining the relative industrial strength it possessed previous to the last war and in this the Lehigh Northampton slate district, the leading one in the country, should be the chief beneficiary.2


By the end of World War II, the slate industry was already seeing the slow slide downward. With the passage of the Federal Aid Highway Act of 1956 a new and bigger threat which was looming on the horizon and which was not associated directly with the material or its fabrication. The slate industry had always had an important, although strained, relationship with the railroads since, due to the weight of the product it needed a system of transportation that exceeded what was possible on the roads. The Federal Highway Act was not a direct threat to the slate industry but was ultimately what lead to the demise of the railroads which in turn was one of the last disincentives for the industry. In 1930 there were still almost 30 functioning slate businesses in the district, but by 1965 that number had dropped to 10.

The word "Slate" is tied to the common history of the entire state of Pennsylvania for more reasons than just the Slate Belt. For Philadelphians, but also for the entire state, one of the most important buildings in state history is known as the "Slate Roof House". This building, built in 1687 and demolished in 1867, was located in Philadelphia and was the last standing building tied to William Penn, founder of the state. It was the building that he wrote and issued his "Charter of Privileges," a progressive framework for Pennsylvania’s government that became the model for the United States Constitution and is still the basis of free governments all over the world. Clearly the building had a slate roof but it is more likely that slate for the earliest roofs of Philadelphia may have come from Peach Bottom instead of the 'Slate Belt' because of its location along the Susquehanna River for transportation reasons.

In its subsequent growth the district suffered the depressions and revivals experienced by the slate industry of the country as a whole. The introduction of channelling represented a marked advance and served as a stimulus; in 1863 it was first practiced in Vermont and probably reached Pennsylvania a decade later.

Geological Survey of Pennsylvania. 1883. The Geology of Lehigh and Northampton Counties. Harrisburg,: Board of commissioners for the Second geological survey,.