In October 1877, Bench Mark "A" was cut on the water table of the recently rebuilt courthouse in Hagerstown, Maryland. It became the beginning point of a transcontinental level line that went by way of Williamsport and then along the C&O Canal to Hancock in one month, though the line did not extend from the Atlantic to Pacific Oceans until 1904. Bench Mark "A" was later included in leveling surveys conducted in 1931, 1941, and 1979, remained very stable in relation to other nearby marks, and was chosen for a releveling project completed in 1988.
