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On Friday, August 23, 1861, Allan Pinkerton apprehended Rose Greenhow for spying and placed her under house arrest.
Maria Rosatta O'Neal was born on a farm in southern Maryland in 1817. Her father was murdered by his slaves when Rose was just a child. The family became destitute. When Rose was 14, she and her sister Ellen went to live with an aunt, Maria Ann Hill, who ran the Congressional Boarding House across the street from the Capitol.
The boardinghouse was a center of Washington society. Senators, congressmen, and other dignitaries lodged there, including John C. Calhoun, who was an important influence on Rose, transforming her into a self-described "Southern woman, born with revolutionary blood in my veins."
Rose was initially snubbed as a nobody, but soon found her place in Washington society. When she was 18, she married one of Washington's most eligible bachelors, Dr. Robert Greenhow. He had a law degree and a medical degree and was one of the highest-ranking members of the State Department.
When the Civil War began, Rose was a widow and a grande dame of Washington society. At the center of everything that was anything in Washington, Rose soon was at the center of a vast espionage network. She was now in her mid-40's and still a striking beauty. She used her "almost irresistible seductive powers" to learn everything she could about General Irvin McDowell's army and passed the information along to General P. G. T. Beauregard in Virginia.
Acting on a tip, Allan Pinkerton, the head of the new Union Intelligence Service, placed Greenhow under surveillance. On the evening of August 22, Pinkerton witnessed a Union officer giving military information to Greenhow. She was arrested the next day. A search of her house turned up a diary with several pages of notes, copies of orders from the War Department, and other incriminating documents.
Although under house arrest, Greenhow barely slowed her espionage activities for the Confederacy. In January of 1862, she would be transferred to Old Capitol Prison.