The Washington Monument: A Striking Story

Jul 30, 2019

The papers of Thomas Lincoln Casey, the U.S. Army Corps Chief of Engineers who supervised the completion of the Washington Monument, include reports, sketches, calculations, and letters that shed light on the risk posed by lightning to the world’s highest structure.

Top of the Washington Monument, setting the capstone

The Washington Monument was dedicated on February 21, 1885. At the time, it was the tallest man-made structure in the world, capped by the largest single casting of aluminum. Aluminum was as valuable as silver in the 1880s. So why was such a supposedly precious metal set at the top of the obelisk?

The aluminum pyramidion served as a way to protect the monument from lightning strikes. The papers of Thomas Lincoln Casey shed light on the risk posed by lightning to the world’s highest structure.

Washington Monument, Project for a Marble Pyramidion, No. 3

That old adage that lightning never strikes the same place twice was disproved in 1892 by a custodian at the Washington Monument named John Hawkins when he wrote a postscript to his report to Casey:

Since writing the above, I have learned from the Watchman who was on duty at the time, that the Monument was struck a second time about 5-40, when the current seemed to leave the column at the same place and explode on the floor.

Indeed, several reports to Casey relate recurring meteorological events at the Washington Monument. The sounds described by workmen when lightning struck the monument varied. For example:

Torrey says it exploded like a pistol shot; O’Day says like a big fire cracker, and was as large as a cannon ball; while Quinn and Madigan describe the explosion to have been like a rifle shot; Cook says the explosion was like a big pop (large fire cracker) and looked like a rocket when it comes down.

On June 29, 1892, Hawkins made note in his report of another fantastic strike experienced from within the monument by both workmen and visitors:

The electric current jumped off the iron column about 20 feet from the floor, and in the form of a ball of fire as large as one’s fist, it struck the floor plate and exploded making a sound like discharge of a gun.

Reports like these offer a glimpse into many of the fascinating Washington, DC, projects that Thomas Lincoln Casey oversaw. Other of his projects include the Washington Aqueduct; the State, War, and Navy Building (now known as the Eisenhower Executive Office Building); and the Thomas Jefferson Building, Library of Congress.

In September 2017, Historic New England secured a $64,415 grant from the National Historical Publications and Records Commission (NHPRC) to support a two-year, $133,878 project to digitize papers related to Casey’s work (over 37,500 pages). Historic New England will pilot a crowdsourcing program to engage the public in efforts to transcribe the digitized records.

The Casey Family Papers covered by this grant include 55.13 linear feet of material divided into four components: Thomas Lincoln Casey’s papers; major engineering and architectural projects in Washington, DC, worked on by both Thomas Lincoln Casey and his son Edward Pearce Casey; the correspondence between Thomas Lincoln Casey and President Rutherford B. Hayes; and Edward Pearce Casey’s papers. Edward Pearce Casey bequeathed the Casey Family Papers along with Casey Farm in Saunderstown, Rhode Island, to Historic New England.