Shropshire was established during the division of Saxon Mercia into shires in the 10th century. It is first mentioned in 1006. After the Norman Conquest it experienced significant development, following the granting of the principal estates of the county to eminent Normans, such as Roger De Montgomery and his son Robert de Bellême. The Coalbrookdale area of the county is designated "the birthplace of the Industrial Revolution", due to significant technological developments that happened there.