This book is an historical analysis of the Union artillery at the Battle of Gettysburg. It examines the significance of the Union artillery's contribution to the Federal victory. This book explores all aspects of the tactical employment of the Union artillery on the first and last days of the battle. A brief description of the evolution of artillery organization in the Army of the Potomac prior to the battle of Gettysburg is included. This is followed by the chronological presentation of the tactical employment of artillery during the battle. First its employment in the meeting engagement on 1 July is examined, followed by a study of its use on the final and decisive third day when Union forces fought a setpiece defensive battle. Among the conclusions arrived at during the course of this study are these: That the Army of the Potomac's corps artillery brigades and army artillery reserve proved to be responsive and efficient organizations in fulfilling their fire support mission, and when coupled with the skillful use of artillery and aggressive leadership by the Army's Chief-of- Artillery, Brigadier General Hunt, were crucial to the successful employment of the Union artillery forces. This book concludes that the Union artillery under the command of Brigadier General Henry Hunt had a decided and positive influence on the Federal victory by successfully employing its corps artillery brigades and army artillery reserve as part of a combined arms force.