This thesis is an investigation of the use and misuse of physical intelligence by Union General George B. McClellan during his 1862 Virginia Peninsula Campaign. Civil War historians have yet to consider what role maps and their accompanying reports played in both the planning and execution of the Campaign. This neglect has led to incomplete conclusions regarding the important question of why the Peninsular campaign failed. General McClellan would later explain that poor physical intelligence resulted in the failure of the Army of the Potomac to take Richmond. From an examination of the original reports and maps of the region, it appears that McClellan was only partially justified in this conclusion. While McClellan's maps were incomplete and in some cases possessed glaring errors, reports of the Peninsula's topography and environmental conditions were remarkably prophetic. That McClellan chose to ignore these reports raises questions concerning the quality of his generalship.