He served as a Union Army officer during the American Civil War and was wounded during two major battles.

At age 20, he began trading horses, taking them east to the Boston and Long Island markets.

In 1856 he entered a partnership with H. S. Allen of Chippewa Falls to set up a stage coach line between the two settlements, and built much of the road between the two.

Mr. Allen was selected by Governor Alexander Randall to serve as the first district attorney of the county.

At the outbreak of the American Civil War, he was commissioned colonel for the 16th Wisconsin Volunteer Infantry Regiment.

His second-in-command was Lieutenant Colonel Cassius Fairchild, whose brother, Lucius, would go on to become the first three-term Governor of Wisconsin.

Colonel Allen's wound was in his arm, and he was able to recuperate with the Regiment as they stationed in the vicinity Pittsburg Landing.

At this Second Battle of Corinth, they again conducted orderly retreats to strong defensive positions, then repelled waves of Confederate attackers.

After the surrender of Vicksburg, however, Colonel Allen, who was still suffering from the effects of his wound taken at Shiloh, chose to retire.

Colonel Allen returned to his private affairs after the war and resumed operation of his several stores in Pepin.