Nehemiah Marks was born in Derby, Connecticut, on 9 October 1746. He was the son of Mordecai Marks (1706-1771), a Sephardic Jew who emigrated from London, England, in 1721 and became a prosperous merchant. He converted to the Anglican faith and in 1729 married Elizabeth [Hawkins] of Derby, Connecticut. Soon after the Revolution began, Nehemiah Marks went to New York where it is believed he carried despatches for the British army. He served as a captain in the Armed Boatmen, a Loyalist corps, with a commission dated 5 October 1782. His commission as a lieutenant in the Maryland Loyalists, dated 1 October 1783, can be found among the papers of his son, Nehemiah Marks, Jr. With the evacuation of New York City, Nehemiah Marks, Sr. was forced to seek refuge in Nova Scotia, and on 1 November 1783, he was appointed a captain in the Nova Scotia Militia for the District of Port Mouton, and charged with the responsibility of settling his men and their families. The refugees remained at Port Mouton for the winter of 1783, but in 1784 Captain Marks decided to move to the Falls of the St. Croix River (St. Stephen, New Brunswick), and a number of his men chose to accompany him. On May 23, 1784, a group of about 200 including men, women and children led by Capt. Nehemiah Marks, steered up the St. Croix River to the head of tide and landed on the Canadian banks of the St. Croix River.
For their loyalty, King George III granted them land, which over time they made prosperous. A large community grew around shipbuilding and lumbering industries, which would eventually become the Town of St. Stephen.
In 1770, Nehemiah Marks married Betsy (Elizabeth) Hawkins (1751-1812), the daughter of Abraham Hawkins (b.1725) and his wife, Elizabeth Basset (b.1728) of Derby, Connecticut. Eight of their children are known to have survived, including: Elizabeth Ann (b.1772), Betsy (b.1774), Hannah (b.1776), George Beckwith (b.1778), John, Nehemiah (1794-1853), Rebecca, and Abraham Hawkins (b.1796). When Nehemiah Marks died in 1799 at the age of fifty-two years, he left an estate that included a house and a store in St. Stephen, a large tract of land on which much of the present Town of St. Stephen is built, and several hundred acres of woodland.