Greenstone Slate Company is a third generation Hill family business with quarries and facilities operating in Vermont and New York State. Most of these quarries share a similar history since slate mining was a cottage industry for local construction from the Colonial Era until after the Civil War. Until the advent of a viable railroad system, roofing slate production was extremely limited due to the difficulty of transporting heavy stone to eastern cities. After the Civil War the railroad line from New York City to Albany was upgraded and extended into the slate-producing regions of Vermont. Greenstone's present Poultney, Vermont quarries were divided into several leases; the largest of which was conveyed to the "Auld and Conger Slate Company," a Welsh business around 1882. Production from the leases increased steadily for the next thirty years and reached its peak around 1915 when the Poultney quarries produced 20,000-30,000 squares of roofing slate per year with a work force of several hundred employees.