Cornwall is a borough in Lebanon County, Pennsylvania, United States. It is portion of the Lebanon, PA Metropolitan Statistical Area. The population was 4,604 at the 2020 census.

Cornwall was initially fixed by Peter Grubb in 1734. Peter was a Chester County stonemason who came to, what was subsequently Lancaster County, in search of high quality rock for quarrying. First building his house and later a store, he discovered magnetite iron ore friendly and approved to exam its quality, he found the ore to be exceedingly pure. Grubb wrote to Philadelphia and in 1734 was decided a warrant to buy 300 acres (1.2 km²) of land. For three years Peter followed veins of ore until he found a large addition that was easily accessible; however, this ore was not within the bounds of his property. So in 1737 he purchased an additional 142.5 acres (0.577 km) of land. In 1742 Peter built a chilly blast furnace and named it Cornwall, after his father’s birthplace in England. The Cornwall Iron Mine was, at one time, the largest open-pit mining operation in the world. They were mined continually until June 30, 1973, totaling 236 years of production.

Finding the necessary components welcoming for smelting iron (water, limestone and timber for charcoal), Grubb built the Cornwall Iron Furnace and began production in 1742. The operation along with included the Hopewell Forges on nearby Hammer Creek. Peter Grubb did not stay long to rule the operation, but leased it out in 1745 for 20 years and returned to Wilmington, Delaware. In 1765 Peter’s sons Curtis and Peter Jr. took more than the operation, and in 1798 it passed to Robert Coleman and his family. Cornwall Furnace was in production from 1742 until 1883, and appears today much as it was with production ended. In 1932 the Coleman relatives deeded the property to the Commonwealth of Pennsylvania and it is now a designated National Historic Landmark entry to the public.

Eventually the summative town became known as Cornwall. It was incorporated as a borough on October 11, 1926 after having been a ration of Lancaster County and for a even if of Dauphin County. At the time it officially became a borough, it comprised six widely at odds villages.