When Tryon left North Carolina in mid-1771 to assume the position of British royal governor of
New York, Sauthier accompanied him there, and was appointed surveyor for the Province of New York by Tryon. During this period, Sauthier was also instrumental in surveying the boundary between New York and
Quebec. In 1776, Sauthier surveyed and mapped
Staten Island, New York, for British
General William Howe, and surveyed and mapped
Fort Washington on
Manhattan Island after troops under the command of
General Hugh Percy attacked and captured it. General Percy retained Sauthier on his staff when he commanded the British forces holding
Rhode Island. In May 1777, when General Percy returned to his familial home at
Alnwick Castle in England, Sauthier accompanied him, and was employed as Percy’s secretary. ==Death==