Maria Isabella Boyd was born in 1844 in Martinsburg, Virginia, now West Virginia, and sent to a Baltimore finishing school at 12. On July 4, 1861, when Union soldiers came to raise a flag at her family’s home and one insulted her mother, the 17-year-old shot and killed him. A military board cleared her, but sentries watched the house. She charmed the officers posted there, including Captain Daniel Keily, wrote what they let slip in cipher, and had Eliza Hopewell, a woman enslaved by her family, carry the messages past checkpoints in a hollowed-out watch case.

In May 1862 at Front Royal, she listened through an enlarged knothole as General James Shields planned to move troops east, then used forged passes to ride through Union lines with the news. Stonewall Jackson took Front Royal on May 23 and thanked her in a handwritten note. Arrested at least six times and tracked by Allan Pinkerton’s men, she was exiled in 1864 after her blockade runner was captured, and in England she married Samuel Wylde Hardinge, the Union officer who had detained her. She later acted as Nina Benjamin and lectured on her spying until her death in Wisconsin in 1900.

• Her memoir’s account of bullets piercing her skirt as she ran between the lines at Front Royal is likely embellished.
• Jackson awarded her the Southern Cross of Honor and honorary ranks of captain and aide-de-camp.
• Betrayed by a lover in July 1862, she was held in Washington’s Old Capitol Prison for a month.
• Newspapers called her the Siren of the Shenandoah and the Cleopatra of the Secession.
• She died of a heart attack at 56 while on a speaking tour, and Union veterans served as her pallbearers.