The Coplay Cement Company Kilns in Coplay, Pennsylvania preserve nine brick Schoefer vertical kilns built in 1892 and 1893 as part of Mill B, a more efficient plant for making Portland cement. Their continuous-operation design improved on older dome kilns, though rotary kilns soon surpassed them and they closed in 1904. The site is closely linked to David O. Saylor, a founder of the company and the first American patentee of Portland cement, whose stronger product helped reshape construction. It also reflects Lehigh County’s natural advantages and the Lehigh Valley’s rise as a major center of the nation’s Portland cement industry.