It sent out 8,000 - 12,000 squares of roofing slate annually .
In 1843 , the Bangor & Piscataquis Slate Company opened with 60 employees .
Bangor & Piscataquis Slate Company sent out 8,000 - 12,000 squares of roofing slate annually .
In 1843 , the Bangor & Piscataquis Slate Company opened with 60 employees .