The Washington Monument was erected to honor the United States' first president and for more than 130 years have stood at a height of 555 feet and 5 1/8 inches. That was up until government surveyors stepped in and made a new official measurement for the monument's height.
The National Geodetic Survey conducts measurements accurate up to one millimeter. Working with standards set by the Council of Tall Buildings and Urban Habitat, chief geodesist Dru Smith and colleagues measured the Washington Monument and found its actual height to be 554 feet and 7 11/32 inches. With this measurement shorter than the official figure used for more than a century, does this mean the monument shrunk?
Not necessarily.
Smith explained that the Washington Monument essentially did not change its height. The new survey yielded a different measurement mostly because it used a different base point compared to what was used in 1884 when the monument was completed.
The original measurement done by Lt. Col Thomas Casey was believed to have utilized four brass markers as a base point. These markers are still in place but they are now about 9 inches below the ground from each of the monument's corners. It is possible that they were visible at ground level in the past. With a new plaza constructed recently around the Washington Monument, what was ground level has certainly changed over the course of time.
Measurements were made back in 1999 and 2014 using the brass markers as the base point and showed that the original numbers from 1884 were incredibly accurate as the same figures were recorded.
The only real reason noted by both old and new measurements for a change in height was that the tip of the monument shaped to be a pyramid has been rounded off. The change in shape was reported as early as 1934, which surveyors attributed to frequent lightning strikes melting the aluminum tip.
"We were able to determine about 3/8 of an inch had been melted off from the very top," said Smith.
From 1884 to 1889, the Washington Monument enjoyed the distinction of being the tallest structure in the world, only to be overshadowed by the Eiffel Tower in France. Still, the monument is the tallest structure in the U.S. capital, where building heights are strictly restricted.
Despite the new measurements being made official, the National Park Service has said it will not be changing descriptions in its brochures or other documents. However, the Service will be using the new measurements to keep tabs on any changes involving the Washington Monument's compression, tilt or height.
