During the century 1770–1870, production was between 15,000 and 20,000 tonnes. In the 1870s, it rose to 40,000 tonnes and exports of pig iron from the Österby ironworks became significant. In order to facilitate shipments of ore Dannemora Hargs Railway ("Dannemora–Hargs Järnväg") was built between Dannemora mines and Hargshamn in 1878. During the 20th century, production was 50,000 tonnes, but a strike in 1927 stopped operations entirely. Only in 1935 was it resumed. 1955 a new facility, with sorting plant and concentrator was finished and the annual production reached 600,000 tons. During the latter part of the 1970s, output decreased but still amounted to about one million tonnes of crude ore, of which the bulk was exported.