I am the author of a book about the Pennsylvania hemp industry. The book is called Hempstone Heritage. The hemp industry was particularly strong in Lancaster County which is where I'm from. That is why we have East and West Hempfield Townships. Between the years of 1720-1870 there were over 100 water-powered hemp mills for processing hemp fiber in Lancaster County alone and there were dozens more in neigboring counties. There were almost as many oil mills for processing hempseed oil as there were for processing the fiber. The distinct conical shaped millstones used in the hemp mills are called "Hempstones". If you want to see a picture of the stones, check out my web site - HempstoneHeritage.com