Allan Pinkerton, The spy in the rebellion; being a true history of the spy system of the United States Army during the late rebellion, revealing many secrets of the war hitherto not made public, compiled from official reports prepared for President Lincoln , General McClellan and the Provost-Marshal-General .

It is needless to relate the valuable items of information which I was enabled to glean upon this journey-information which in later days was of vast importance to the Union commanders, but which at this time would only burden a narrative of the events which they so ably assisted to successful results.

Here, as in many other places, I found that my best source of information was the colored men, who were employed in various capacities of a military nature which entailed hard labor. The slaves, without reserve, were sent by their masters to perform the manual labor of building earthworks and fortifications, in driving the teams and in transporting cannon and ammunition, and, led by my natural and deep-seated regard for these sable bondsmen, I mingled freely with them, and found them ever ready to answer questions and to furnish me with every fact which I desired to possess.

Here and there I found an unassuming white man whose heart was still with the cause of the Union, but whose active sympathy could not at this time be of service to the country, as he dared not utter a voice in defense of his opinions. From all these sources, however, I was successful in posting myself fully in regard to the movements and intentions of the rebel authorities and officers, and, as I believed, had also succeeded in concealing my identity.