The datum is defined by the observed heights of mean sea level at the 26 tide gauges and by the set of elevations of all bench marks resulting from the adjustment. A total of 106,724 kilometers of leveling was involved, constituting 246 closed circuits and 25 circuits at sea level.
George Washingtonâs Mount Vernon is located roughly 15 miles south of Washington, D.C. and 8 miles south of Alexandria, Virginia on the banks of the Potomac River, at the southern end of the George Washington Memorial Parkway.
Todayâs residents occupy a neighborhood at the eastern end of the downtown convenience corridor, next door to Chinatown, Penn Quarter, Logan Circle and Capitol Hill. In addition to the Convention Center, the Mount Vernon Triangle is home to the restored Andrew Carnegie Library which houses the DC Historical Society.