The Battle of the Crater

[Part of Federal Line of Works showing bombproof tents occupied by U.S. Colored Troops in front of Petersburg, Va., Aug. 7, 1864]

For several weeks, Union troops with mining experience dug a tunnel from their trenches to enemy lines. They packed the chamber at the end of the tunnel with explosives and blew it up on July 30, 1864.  The explosion created a hole that was “more than 170 feet long, 60 feet across, and 30 feet deep.”
Brendan Wolfe. “Battle of the Crater,” Encyclopedia Virginia, retrieved February 23, 2020

Additional sources:
— “The Crater,”  American Battlefield Trust, retrieved February 23, 2020
— “Petersburg: The Crater,” National Park Service, retrieved February 23, 2020