|The Hillsborough Mills is locally significant under Criterion A, Industry, for its associations with manufacturing in Milford, New Hampshire. From the mid 19th to the mid 20th century, the industries housed in this complex served as important local employers for workers in both Milford and nearby Wilton. Constructed in 1866, just after the end of the Civil War, the mill was initially organized by local investors for the manufacture of woolen carpets. When the carpet mill failed, the property was reorganized and purchased in 1874 by new investors from the manufacturing centers of Nashua and Lowell and produced carpet yams, bed blankets and horse blankets. Although the mill was expanded and flourished for a number of years, it closed in 1901, unable to compete with larger companies. The Hillsborough Mills were sold that year to a group of out-of-town woolen manufacturers including William G. Abbott of Philadelphia. The Hillsborough Mills flourished under the management of Abbott and his two sons, William Jr. and Edward James Abbott, accomplished scientists and inventors. The company became known for its worsted weaving yams and the success of the Hillsborough Mills led to the development of two other industries- Abbott Worsted Mill and Abbott Mill in nearby Wilton. At its peak 300 workers were employed at the Hillsborough Mills with another 200+ at the other two factories. Although the Hillsborough Mills closed about 1970, Abbott family members retained ownership until 1979 and continued to feature prominently in local affairs into the late 20th century. Despite the loss of a wooden dye house, the filling of the canal and incremental changes to the buildings, the complex retains integrity of location, design, setting, materials, workmanship, feeling and association. The mill's period of significance is 1866-1963. The first date corresponds to the mill's original date of construction; the latter reflects the 50 year cut off of the National Register.