During 1791–1792, Ellicott also surveyed the future city of Washington, which was located within a relatively small area at the center of the Territory of Columbia along the northern bank of the Potomac River at the confluence with its Eastern Branch (known today as the Anacostia River). Ellicott also served under the Commissioners' supervision in this effort. He first worked with Pierre (Peter) Charles L'Enfant, who had prepared the initial plans for the future capital city during the early months of 1791 and had presented one of these early plans to President Washington in August of that year (see L'Enfant Plan).