Spy Marie Isabelle "Belle" Boyd (May 9, 1843-June 11, 1900) was born in Martinsburg, the daughter of Benjamin R. Boyd, a merchant. In 1853, Mr. Boyd purchased land at the corner of Race and Spring streets and built the most architecturally significant Greek Revival mansion in Martinsburg.

Belle was sent to Mount Washington School in Baltimore in 1856, graduating at age 16. The Boyds moved from their Race Street mansion to the 500 block of South Queen Street in 1859. It was there on July 4, 1861, that Belle shot a Yankee soldier and started her spy career. She was imprisoned twice. She moved to Front Royal, Virginia, after being acquitted in the soldier's death. From Front Royal she carried news of Union plans to Confederate Gen. Stonewall Jackson during Jackson's successful 1862 Shenandoah Valley campaign. She returned to Martinsburg and continued to spy.

In 1864, Belle Boyd married Samuel Wylde Hardinge Jr. A former U.S. Navy officer who had been her captor, Hardinge had disgraced himself by falling under Boyd's influence and allowing an important prisoner to escape. The couple had one daughter before Hardinge died, probably in England between the end of 1865 and July 1866. Boyd married the second time in 1869 to John Swainston Hammond, and they had four children before divorcing in 1884. She married her third husband, Nathaniel High, in 1885.

Boyd wrote a book, Belle Boyd in Camp and Prison, while she was in London in 1865. It was republished many times. She made a living for her family as an actress. She died in Kilbourn, Wisconsin, where she is buried. Boyd's childhood house at 126 East Race Street in Martinsburg and the cottage in Front Royal, Virginia, are now museums.