Mayfield Fort was a six-sided enclosed earthwork built by hand in just a matter of months, with an open central space 200 feet in diameter large enough for three small buildings. Trenches lined the inside, and the dirt removed from them was formed into parapet walls fortified with large logs and intertwined small branches to prevent erosion, all moved manually. Sixteen gun openings were set at regular intervals around the fort, each intended to hold a large naval gun captured from the Gosport Navy Yard in Norfolk. Set high on ground with open fields of fire, the fort was part of the earthwork defenses built here primarily to protect a vital supply line. In March 1862, the N.Y. Morning Herald called it the monster Manassas, which for eight months had been the fright and bugbear of the country, while also observing that the planking in the embrasures suggested that no siege guns had ever been in position.