Benjamin King Hagger was listed in the first city directory of Boston in 1789 as "a mathematical instrument maker" with an address on Ann Street; he was only 20 years of age at this time.
On November 10, 1793, Benjamin King Hagger, "mathematical instrument maker," purchased land with buildings on Prince Street near Snow Hill Street from one Peter Greene. Two years later, on December 1, 1795, Hagger, now listed simply as a "merchant," purchased a brick house, a wooden house, and a shed with land from William Ballard, a tailor of Framingham and an heir of Samuel Ballard. The property was located on the east side of North Street, south of Mill Creek. At the time of purchase, Hagger mortgaged the property to Ballard, and also mortgaged to him the house and land previously purchased from Greene.
Hagger was listed as a ship chandler in the following year when on March 24, 1796, he deeded part of his land on Prince Street to William and George Hillman, minors.
On June 22, 1796, three months later, Hagger, now listed as "mathematical instrument maker, and ship-chandler" deeded to a mariner named Thomas Wallis a house and land that formed part of his original purchase near Copp's Hill from Peter Greene. Then on July 21, 1796, he purchased from William Ballard all his right to the brick house and land on North Street (Ann Street), at the same time mortgaging the property to William Ballard, Jr., of Framingham. This mortgage was cancelled on April 11, 1798.[112]
These negotiations took place before marriage. A report of the Record Commissioners of Boston, states that "William King Hagger of Boston and Mehitable Ballard of Framingham were married October 6, 1796." The entry appears to be in error because the marriage intentions had read "Benjamin King Hagger." It is presumed that Mehitable was the daughter of William Ballard, the tailor of Framingham, from whom Hagger had bought his house on Ann Street, south of Mill Creek.[113]
Benjamin King Hagger is listed in the city directory of Boston for 1798 as a "mathematical instrument maker" on Ann Street. This, however, is the last listing for his name in Boston, as his name does not appear in the 1803 or subsequent directories.
Shortly after 1798 Hagger appears to have left Boston together with his wife, and it is probable that he established himself as an instrument maker in another Massachusetts community, at present unknown. In about 1816 Hagger moved with his family to Baltimore and continued his instrument-making business.
The records of the 1850 Federal census of Baltimore indicate that two of Hagger's sons, John W. and William G. Hagger, had been born in 1800 and 1806 respectively, in Massachusetts, presumably in the community to which Hagger had moved from Boston before moving once more to Baltimore.
According to Matchett's Baltimore directory for 1824, Hagger was a "mathematical and optical instrument maker" with a shop at 57 South Street. His advertisement in the directory stated that he
Respectfully acquaints his fellow citizens that he executes all orders in the line of his business with punctuality and confidently professes to give satisfaction to his employers, from the experience of a regular apprenticeship and 37 years practice.