Jenifer was born in 1723, in Port Tobacco Village, Maryland. His father, Dr. Daniel Jenifer, was of English ancestry, and his mother, the daughter of Samuel and Elizabeth Hanson and the sister of John Hanson, was a direct descendant of a Swedish Colonel Hanson who died with Gustavus Adolphus on the battlefield of Lützen. John, the son of Colonel Hanson, emigrated from Sweden to America in 1642.
Jenifer, the origin of whose distinctive name is unknown, was possessed of unusual wealth for the time and made his home on his large estate, known as "Stepney, " in Charles County. Besides serving as agent and receivergeneral for the last two lord proprietors of Maryland, he held many offices of public trust. In his young manhood he was justice of the peace of his home county, and, later, of the western circuit of the province. In 1760 he was placed upon the commission for the settlement of the boundary dispute with Pennsylvania and Delaware. In 1766 he was made a member of the provincial court, and from 1773 until the opening of the Revolution he sat upon the governor's council. Though at first inclined to be conciliatory and desirous of peace with England, he at length took a stand for independence and in 1775 was chosen president of the Maryland Council of Safety and showed great activity in securing aid for the Revolutionary cause. When the state government was set up in 1777 he was made president of the Senate. The following year Jenifer was elected to the Continental Congress, of which he was a member until 1782, serving on various committees, including the admiralty board and the committee to consider the cession of western lands. Nationalistic in bent, he favored a permanent union of the states, opposed the emission of paper money, and desired that Congress be given the power to tax. Beginning in 1782 he was for some years intendant of the Maryland revenues and financial agent of the state. He was likewise one of the commissioners from Maryland who, in 1785, met, first at Alexandria and then at Mount Vernon, to settle with Virginia the question of navigation of the parts of Chesapeake Bay and the Potomac shared by the two states. Two years later he was sent as a delegate from Maryland to the Federal convention in Philadelphia, but he played only a very minor part in framing the new constitution. The most important stand he took was for a three years' term for members of the House of Representatives, for he felt that too frequent elections would cause popular indifference to civic duties and would make men of prominence unwilling to assume office. He favored the completed constitution and signed it, and when Luther Martin declared that he would be hanged if the people of Maryland would approve the document, Jenifer humorously advised him to remain in Philadelphia lest he hang in his home state. Jenifer's death took place at Annapolis, on November 16, 1790.
Jenifer never married but lived in jolly bachelorhood at his estate, "Stepney. "
