Dorothea Quarry commenced working in the early 1820s, though there were a number of smaller workings on or near the site before this. By 1848 it had become the dominant quarry in the area, employing 200 men and producing 5000 tons of finished slate. Production peaked in 1872 at 17442 tons. In the 1930s over 350 men were employed at Dorothea. Production dropped significantly after the start of World War II and the quarry closed in 1970.
