The inhabitants of Upper Merion derived quite a bit of wealth from its mines and quarries. The marble mined in Upper Merion ran in a long, narrow, perpendicular seam, extending down a considerable depth. The deeper the marble was obtained, the better its quality. KoP Marble was used in the more opulent homes in the northeastern US. It was used primarily for monumental public building projects from 1790-1860, especially those designed in the Greek Revival style. It replaced wood as the building material of choice. By the end of the 19th century the demand for the material had diminished and the quarrying of marble ceased.
Source: King of Prussia Historical Society
E-History Fact published 1/16/2015 Upper Merion Township E-Newsletter