In the early years of the Colonies, nearly all roofing slate
was imported from North Wales. It was not until 1785 that
the first commercial slate quarry was opened in the United States,
by William Docher in Peach Bottom Township, Pennsylvania.
Production was limited to that which could be consumed in local
markets until the middle of the nineteenth century. Knowledge
of the nation's abundant stone resources was given commercial
impetus at this time by several forces, including a rapidly growing
population that demanded housing, advances in quarrying technology,
and extension of the railroad system to previously inaccessible
markets. Two additional factors helped push the slate industry
to maturity: the immigration of Welsh slate workers to the United
States and the introduction of architectural pattern and style
books. Slate production increased dramatically in the years
following the Civil War as quarries were opened in Vermont, New
York, Virginia, and Lehigh and Northampton Counties, Pennsylvania.
By 1876, roofing slate imports had all but dried up and the United
States became a net exporter of the commodity.
The U.S. roofing slate industry reached its highest point in
both quantity and value of output in the period from 1897 to 1914.
In 1899, there were over 200 slate quarries operating in 13 states,
Pennsylvania historically being the largest producer of all. The
decline of the U.S. roofing slate industry began c.1915 and resulted
from several factors, including a decline in skilled labor for
both the fabrication and installation of slate and competition
from substitute materials, such as asphalt shingles, which could
be mass produced, transported and installed at a lower cost than
slate. Only recently, with the increasing popularity of historic
preservation and the recognition of the superiority of slate over
other roofing materials, has slate usage begun to increase.