Shallus was the son of German immigrants, Valentine Schallus and Frederica Catherina.[2][3] His brother Thomas Shallus was a mapmaker. He was born a year after his father Valentine immigrated to Pennsylvania and was a volunteer in the Revolutionary War. During the Revolutionary War, Shallus fought in Canada and became a quartermaster of Pennsylvania's 1st Battalion. Shallus also assisted in the outfitting of a privateering vessel, the Retrieve.[4]
Shallus' name appears nowhere on the document itself, but an investigation into the identity of the Penman in 1937 for the 150th anniversary of the Constitution revealed the identity of the transcriber. Shallus was paid $30 (equivalent to US$726 in 2023) for his engrossing work, a sum recorded as for "clerks employed to transcribe & engross."[4] The effort consisted of copying the Constitution on four sheets of parchment made from treated animal skin (either calf, goat, or sheep; in 1987 the supervising conservator at the National Archives said, "We don't know which") and measuring 28 3/4 inches by 23 5/8 inches, probably with a goosequill and with ink made of iron filings in oak gall that was black when applied but that has now turned brownish.[5] Shallus engrossed the entire document except for the list of states at the end of the document, which are in Alexander Hamilton's handwriting.[4]
Shallus married Elizabeth Melchor, sister to Col. Isaac Melcher, Barrack-Master-General of the Continental Army. Her obituary from the Democratic Press in Pennsylvania from August 3, 1818 notes she was "one of those patriotic Ladies of Philadelphia who first associated together and supplied the suffering soldiers with shirts, stockings, &c. in that eventful period of the revolution, which tried and apalled [sic] even men's souls."
^Irvin Molotsky, "The Constitution: It's 200 Years Old, and It Certainly Has Been Around", New York Times (September 17, 1987), p. 15, quoting Norvell Jones, supervising conservator at the National Archives, and Kenneth E. Harris, a director of preservation at the National Archives.