During the Civil War, a number of women were arrested for intelligence work on behalf of the Confederacy, but none achieved the celebrity of Rose O’Neal Greenhow. Her story is filled with intrigue, love, and tragedy.
As a teenager, Rose O’Neal traveled with her sister to Washington, D.C., where they resided with an aunt who maintained a boardinghouse in the Old Capitol building (later, ironically, to become the Old Capitol Prison). There the beautiful young sisters had  the opportunity to associate with many of their aunt’s male borders, many of whom were up-and-coming politicians. In this setting, Rose developed a taste for living an active social life and rubbed shoulders with people in power. At the age of 26, she married  43-year-old Dr. Robert Greenhow, a Virginian, who was both wealthy and socially well placed.
By the time she was in her mid-thirties, Rose was the mother of four daughters and living in the nation’s Capital. Surrounded by the  many advantages that her prestigious husband could offer her, Greenhow became well-known for her beauty, her manners, her gift  for intrigue, and her determination to accomplish whatever she set her heart upon. In 1850, Greenhow and her husband left Washington and traveled west due to the promise of greater financial gains. Instead, an injury led to the early death of Dr. Greenhow  in San Francisco. Rose returned to Washington and gained a reputation as a woman to be reckoned with, thanks to her ability to btain favors, influence members of Congress, and advance her friends’ careers.
As 1860 arrived and sectional tensions increased, Greenhow openly revealed herself to be a staunch supporter of the Confederacy and as the war began, she immediately became an activist for the rebels. She developed a close association "with Lieutenant Colonel Thomas Jordan (alias Thomas John Rayford) of Virginia, a former quartermaster in the United States Army who was in the process of developing an elaborate Confederate spy network in the federal Capital." From Jordan, Greenhow learned the use of a 26-symbol cipher, and "began to exploit her connections with the prominent Unionists for the purpose of eliciting information that she then transmitted in code to relevant figures in the Confederacy." Over time, Greenhow and Jordan enlisted the regular help of various others, forming an extensive spy ring that included both men and women.
Greenhow became best known for her spy work that gave the Confederate army the edge in its first major confrontation with Union soldiers at the first battle of Bull Run in July 1861 as evidenced by the following quote:
An 1863 letter written by General P.G.T. Beauregard – second in command of the Confederate army’s ranking officer, General Joseph E. Johnston, in the summer of 1861 – confirms that on July 10, Greenhow sent an attractive young woman named Betty Duvall to Beauregard’s post at Fairfax Court House, just a few miles from Bull Run, bearing – tightly wound in her chignon a message concerning Union commander Irvin McDowell’s preparation to advance on the Confederacy six days later. General Milledge L. Bonham of South Carolina received the message and transmitted it directly to Beauregard, who notified President Davis and then immediately began preparations to undermine McDowell’s advance. On the sixteenth, Greenhow communicated a second time with Beauregard, who was now encamped with the army near Bull Run. With the help of George Donellan, a former Interior Department clerk, Greenhow sent Beauregard an encoded dispatch containing the news that, as Beauregard later wrote, "the enemy – 55,000 strong, I believe – would positively commence that day his advance from Arlington Heights and Alexandria on to Manassas (near Bull Run), via Fairfax Courthouse and Centerville."
This news Beauregard also forwarded by telegraph to President Davis, who ordered General Johnston, stationed 50 miles away, to bring his troops into the area as reinforcements. While awaiting Johnston’s arrival, Beauregard shifted his own troops to meet the advancing federals, and on July 21, the Union suffered a stunning and humiliating defeat. The following day Greenhow received from Thomas Jordan an expression of Jefferson Davis’s gratitude for her loyal service.

Greenhow continued to transmit intelligence information to the Confederate army. Soon, as a result, her activities led Federal officials to become suspicious. By late July 1861, Allan Pinkerton, the head of the newly formed secret service organization for the federal government ordered close surveillance of the Greenhow home.
The following month, Pinkerton placed Greenhow under house arrest and stationed guards inside the house. Although Greenhow was able to destroy a number of papers, enough was uncovered to incriminate her and heap suspicion upon some prominent Unionist figures that came under her influence. One of these was the powerful senator from Massachusetts, Henry Wilson, who seems to have been one of Greenhow’s primary sources and perhaps even her lover. "(Many interpreters of Greenhow’s papers believe that Senator Wilson was the author of a stack of love letters found in her home)."
"Word spread quickly that federal agents had captured a major figure in Confederate espionage, and a woman," and "on August 26, both the New York Times and the New York Herald smugly reported Greenhow’s arrest." Greenhow remained under house arrest with her youngest daughter, "Little Rose," until she was transferred with her daughter to the Old Capitol Prison, January 18, 1862. For five months, she and her daughter remained at the Old Capitol Prison, now prisoners in the same spot where as a teenager Greenhow had acquired her first taste of social life in Washington. However, even her imprisonment did not deter her from continuing to provide information to Southern loyalists. This prompted Federal authorities to banish her south, where they presumed she could do less harm. On June 2, the New York Times recorded her release and removal under close custody.
Traveling to the Confederate Capital, Greenhow enjoyed praise from various dignitaries to include President Davis and General Beauregard. From that point on, as a last effort, she assumed the "role of blockade runner, in connection with which she traveled to England and France." "There she socialized, tried to drum up foreign support for the Confederacy, and produced her memoir, My Imprisonment, and the First Year of Abolition Rule at Washington, a work that brought the loyalty and good sense of a number of important Union men into question." After some time, Greenhow yearned to return to America where she owned property. With this in mind, and with two thousand dollars in gold in her possession, Greenhow boarded a blockade-runner, the Condor, bound for North Carolina in September 1864.
As fate would have it, tragedy befell Greenhow; therefore, returning to America brought an end to her intriguing story. The still beautiful Rose failed to make it home to the Confederacy. Spied by a Union gunboat in the waters just off the coast near Wilmington, North Carolina, the Condor raced ahead up the Cape Fear River hoping to avoid confrontation. Instead, the Condor ran aground on a sandbar. "Desperate to escape, Greenhow demanded that she be allowed to board a lifeboat, although the weather was ominous." Against the captain’s wishes and advice, Greenhow and two other passengers attempted to make it to shore. "Their lifeboat capsized in the rough water, and within moments, Greenhow, weighed down by her cache of gold, drowned." After her body was recovered the following day, she was laid out in state in a hospital chapel in Wilmington with a Confederate flag for a shroud. She was buried on October 1, 1864.

(Source: All the Daring of the Soldier: Women of the Civil War Armies; Leonard, Elizabeth D; 1999)