Who are the men in the picture shown below with President Abraham Lincoln?

At the outset of the U.S. Civil War, Mathew Brady (a chief photojournalist) dispatched a team of photographers to document the conflict. Alexander Gardner was the top photographer who took this photo of Lincoln at Antietam, Maryland as well as other famous wartime shots.

The man right to Mr. Lincoln's is Allan Pinkerton, founder of the Pinkerton National Detective Agency, whom Lincoln had as head of a personal security detail during the Civil War.

The man to the left of the president is Major General John A. McClernand, a Union general in the American Civil War. As a close friend and political ally of Mr. Lincoln, McClernand was personally given permission to recruit a force to conduct a war operation against Vicksburg, Mississippi.

So, in this instance, this is clearly a photo of Allan Pinkerton, President Abraham Lincoln, and Major General John A. McClernand.