His family's home, The Judge Jeremiah Sullivan House, in Madison, Indiana stands as one of the oldest in the community, a perfect example of Federal-style architecture.

He was the son of Virginia-born attorney Jeremiah Sullivan, who served as a justice of the Indiana Supreme Court and coined the name "Indianapolis" for the new state capital.

He was commissioned as a midshipman and spent the next six years primarily at sea, serving aboard four different vessels, including duty during the Mexican–American War.

[1] In April 1854, he resigned from the Navy and returned home to Indiana, where he studied law, passed his bar exam, and opened a private practice.

During the 1863 Vicksburg Campaign, Sullivan served on the field staff of Maj. Gen. Ulysses S. Grant as the acting inspector general for his army.

In mid-October 1863, he led a column from Harpers Ferry that thwarted an attack on Charlestown, West Virginia, by Confederates under John D. Imboden, driving the enemy up the valley.

He resigned from the army on May 11, 1865, and tellingly was not among the scores of Union generals who received brevet promotions to higher rank at the close of hostilities.