The Great Northern Catskills of Greene County was once home of the world's largest tannery (among many others), established by Zadock Pratt - a congressman and established citizen of the region. With an abundance of eastern hemlocks that produced the tanning acid, or tannins, necessary to preserve the hides that were shipped in from other countries, the Catskills were the ideal setting for tanners to set up shop in the early 19th century.