In 1870, slate was discovered by a resident who had immigrated from Wales, while driving his horse in the countryside of the town. Over the next few decades many slate quarries were created increasing the population of the town, as well as generating a source of income for residents. Because of the large-scale operations, a two foot gauge railway, the Monson Railroad, was created and up to four locomotives were used in the transportation of the slate, as well as transporting passengers to the larger Bangor and Aroostook Railroad in Abbot. The slating industry began to decline after World War I and most of the operations effectively ended. Currently, Sheldon Slate Company is the only operation that exists in the town, although there is a smaller operation selling typically roofing and landscaping slate. The slate from Monson make up the Kennedy headstones in Washington D.C.
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