Rose O'Neal Greenhow was a well-known person in Washington, DC, before the Civil War. President James Buchanan was her close friend. She liked to attend sessions of Congress and Supreme Court hearings. Greenhow would eventually write about her decision to support the South "I had a right to my political opinions. I am a Southern woman, born with revolutionary blood in my veins. Freedom of speech and of thought were my birthright, guaranteed, signed and sealed by the blood of our fathers."
Greenhow was recruited into the spy ring headed by Colonel Thomas Jordan. Soon Greenhow was leading a large network of Confederate spies operating in Washington, DC. Her network included dentists, professors, architects and cooks and spanned as far as New Orleans, Boston and across the ocean to London.
Union generals and politicians continued to be charmed by Greenhow, visiting her well into the war. Even Greenhow's own daughter did not suspect her of being a spy.
Greenhow's relaying of information proved invaluable to the Confederacy victories during the early months of the war. Confederate President Jefferson Davis even went so far as to tell Greenhow "but for without you, there would have been no Bull Run."
Greenhow's luck began to change in August, 1861, when she was arrested for spying by famed detective Allan Pinkerton. She recounted her arrest in her book My Imprisonment and the First Year of Abolition Rule at Washington:
On Friday Aug. 23, 1861, as I was entering my own door on returning from a promenade, I was arrested by two men, one in citizens clothes and the other in the dress of an officer of the United States Army. This latter was called Major Allen, and was the chief of the detective police in the city. They followed close upon my footsteps. As I ascended my steps the two men ascended also before I could open the door and asked "Is this Mrs. Greenhow?" I answered "Yes. Who are you and what do you want?" "I come to arrest you." "By what authority?" The man Allen, or Pinkerton (for he had several aliases) said: "By sufficient authority." I said: "Let me see your warrant." He mumbled something about verbal authority from the War and State Department and then they followed me into the house. By this time the house had become filled with men, and men also surrounded it outside like bees from a hive. An indiscriminate search now commenced throughout my house. Men rushed with frantic haste into my chamber. My beds, my wardrobes were all upturned. My library was taken possession of and every scrap of paper was seized.
The evidence gathered at Greenhow's house is still preserved in the National Archives in Washington, DC.