The Coplay Cement Company kilns were large, industrial structures used for producing cement. Built in the late 19th century, these kilns utilized a process called calcination, where limestone and other materials were heated to high temperatures to create clinker, a key ingredient in cement production. These kilns are notable for their unique design and historical significance in the Lehigh Valley region of Pennsylvania. They represent an important part of the area's industrial heritage and contributed to the growth of the cement industry in the United States during that time.