Hillsborough County, NH

About Hillsborough County, NH

Hillsborough County is the most populous county in the U.S. state of New Hampshire. Its county seats are Manchester and Nashua and is northern New England's most populous county as well as its most densely populated. Hillsborough was one of the five original counties identified for New Hampshire in 1769, and was named for Wills Hill, the Earl of Hillsborough who was British Secretary of State for the Colonies at the time. The county was formally organized at Amherst on March 19, 1771. In 1823, a portion of Hillsborough Country became part of Merrimack County, though the town of Merrimack along the Merrimack River in south-central Hillsborough County was not included in the newly-formed county to the north. Hillsborough County's administrative functions were moved from Amherst to Milford in 1866, and then to the current seats of Manchester and Nashua in 1869.