The Civil War in Maryland was in many ways a microcosm of the events that afflicted the entire nation. As a border state, Maryland held conflicting loyalties between the Union and the new Confederate States of America. Its role in the struggle reflected those divided allegiances as its men, following the dictates of either conscience or kinship, were compelled to choose sides.

While the number of Marylanders who served in the Union and Confederate armies is still the subject of discussion, it is estimated that up to 60,000 of the state's men, both black and white, served in various branches of the Union military; and though the state did not officially recruit troops for Confederate service, as many as 25,000 Marylanders may have fought for the South.

Maryland's Blue and Gray is a collective biography focusing on the 365 men from Maryland who served as captains and lieutenants in the Virginia theater of operations, specifically with the Army of the Potomac's Maryland Brigade and the Army of Northern Virginia's Maryland Line. These soldiers provide a rare opportunity to investigate the backgrounds, military careers, and wartime experiences of a specific group who fought on both sides of the nation's bloodiest and most contentious war. Ruffner examines the effects of the conflict on the officer corps in terms of promotions, morale, and discipline, and on their relationships with the home front, subordinates, and commanders.

Ruffner offers insight into the cultural affinities between the Union and Confederate Marylanders as well as into the nature of the divisiveness that resulted in deadly combat. A groundbreaking study, Maryland's Blue and Gray utilises both military and social history to plumb the motivations, ambitions, and experiences of men from a single state that, like the country at large, was torn asunder.