Cornwall owes its being to Peter Grubb, a 19 year old immigrant who in 1737 came to this area from his home in Delaware in search of building stone and discovered three outcropping deposits of magnetic iron ore. He purchased a total of 442.5 acres of the land for $675.00 and established what was to become one of the world-renowned and most productive iron ore mining operations of all time. Following 236 years of continuous operations, during which time 100 million tons of magnetite iron ore were produced, along with 447,000 tons of copper, plus iron pyrite (and trace elements of gold and silver, the mineral deposit was depleted and the famous Cornwall Iron Ore Mines closed permanently June 30, 1973. An associated by-product contained in the ore was cobalt and Cornwall was the leading producer east of the Mississippi River of this mineral. Twenty-five common and 57 uncommon minerals were associated with the ore, which attracted mineral collectors from around the world.

Cornwall became a Borough on October 11, 1926 after having been a part of Northern Lancaster County and for a while of Eastern Dauphin County and was designated Cornwall Township. At one time Cornwall Township embraced all of the lands, which today are known as West Cornwall and North Cornwall Townships and stretched from Fontana to Rexmont and from Lebanon City boundary line to Lancaster County line. At the time it officially became a Borough, Cornwall was comprised of six widely separated villages. In 2005, it currently consists of 20 separate villages or developments with a total population of about 3,500. Cornwall Borough embraces 9.7 square miles in area (more than the Capitol City of Harrisburg at 9.4 square miles and more than twice the area of Lebanon at 4.6 square miles). It is the largest borough geographically in the continental United States and at the time incorporated in 1926 was deemed the richest because of its iron ore.

Cornwalls heritage is completely that of an industrial complex which flourished for 236 years, generated by the world famous Open Pit Iron Ore Mine, and underground mine at Burd Coleman and another at Rexmont; iron furnaces at North Cornwall, Burd Coleman, and Anthracite Village; ore roasters at Anthracite; an iron ore concentrator plant at Rexmont, which were serviced by three railroads Cornwall RR, Cornwall and Lebanon RR, and Cornwall Ore Bank RR. The former two railroads transported passengers as well until 1929 with the Cornwall RR alone handling more than five million passengers during its operating years. All of the foregoing have disappeared, with the exception of the Cornwall RR Station which in 1972 was remodeled to become the Cornwall Borough Municipal Office (and subsequently enlarged); the Open Pit Mine  now a vast lake containing untold billions of gallons of potable water (which it produces from underground) which overflows into Furnace Creek or is pumped to augment the water supply of another community who purchased that option.

But the most significant and treasured part of Cornwalls beginning history still with us and standing intact in all its historical splendor after 263 years is the Crown Jewel which gave Cornwall its birth and name The Cornwall Iron Furnace. Staffed and operated as a must stop and visit place by the Pennsylvania Historical and Museum Commission, it is a solid stone structure that will probably still be standing for another 263 years or more.