Hammond married Ellen Sarah Sophia Clarke (1833–1905), the sister-in-law of Samuel Warren, in 1874. Hammond survived her by three years upon her death in 1905.
Along with New York architect Alexander Twombly, who was the engineer and draftsman of Forest Paper Company, Hammond designed what is today known as Camp Hammond, set back from Yarmouths Main Street and from which Hammond could see his mill. Twombly also designed several buildings in Boston. Frederick Law Olmsted, who designed Central Park in New York City, designed the gardens of the property. With the Hammonds splitting their time between Boston and Yarmouth, the property became known as the Camp'.
The Hammonds also formed the Antiquarian Society in order to facilitate the 1890 purchase of the North Yarmouth and Freeport Baptist Meetinghouse on Yarmouth's Hillside Street. It became a library and museum, known as the Hillside Library.
Among the many roles Hammond took on without payment was as president of the Yarmouth Water Committee, established in 1895, which sourced its water supply from Hammond Spring on the property of Forest Paper Company. Hammond donated Forest Paper Company land for the 1903 construction of Merrill Memorial Library, on Main Street, which was designed by Alexander Longfellow, a nephew of the poet Henry Wadsworth Longfellow.
Hammond served in the Maine Legislature between 1868 and 1870, was on the Maine Board of Agriculture and the board of trustees of North Yarmouth Academy, was a member of the American Association for the Advancement of Science, the Society of Chemical Industry, the American Institute of Mining, Metallurgical, and Petroleum Engineers, The Society of Arts and Crafts of Boston, the Massachusetts Historical Society, the New England Historic Genealogical Society (from January 1876), The Bostonian Society and the Franklin Institute. He was also a Freemason.
A member of the American Horticultural Society, he was a keen arborist, and his knowledge of trees and plants earned him a place on the Overseers Committee at Harvard Universitys Gray Herbarium between 1888 and the time of his death.
The Hammonds were members of Yarmouths First Parish Congregational Church and Bostons Trinity Church.