When the Scots-Irish established Delta in 1734, the area was still inhabited by the Susquehannock Indians. The Welsh didn't begin to settle in Delta until the mid-19th century when the slate they quarried from the ground started to become an internationally recognized economic commodity. Their story is told in the Old Line Museum. Filled with artifacts, photographs and clothing, the museum helps a visitor to quickly understand what life was like in the 19th century. One of the museum's prized pieces is the world-famous "Slate Clock", a one-of-a-kind creation, made by Humphrey Pritchard, a life-long slate quarrier. The clock stands more than 7 feet tall and 30 inches wide. The museum also emphasizes the Welsh heritage of the Delta area and features Indian artifacts and Maryland and Pennsylvania railroad material. The museum also hosts an annual festival celebrating the culture and heritage early settlers and the slate industry.