[2] At age 17, he began teaching school and had as one of his pupils his cousin Daniel Kirkwood, who later achieved prominence as a mathematician and astronomer.

Summoned from his mill at Coralville and still coated in flour dust, Kirkwood gave a rousing speech at the founding meeting of the Iowa Republican Party in February 1856.

During the Civil War, Kirkwood gained national attention for his extraordinary efforts to secure soldiers and supplies from Iowa for the Union Army.

A strong supporter of President Abraham Lincoln's policies during the American Civil War, he was active in raising and equipping dozens of regiments for the Union Army.

In 1862, he attended the Loyal War Governors' Conference in Altoona, Pennsylvania, which ultimately gave Lincoln support for his Emancipation Proclamation.