Documentation confirms the existence of blowing houses in Cornwall as early as 1402, but the earliest reference for Dartmoor is not found until the early 16th century, though it is likely that they were in use on the moor earlier. In Devon there are many references to blowing mills throughout the 16th and 17th centuries, reflecting the boom time in tin-mining on Dartmoor. However, by 1730 there were only two blowing mills working in the whole of the county: at Sheepstor and Plympton.