With the outbreak of the Civil War in April 1861, Ingalls was reassigned to duty at Fort Pickens in Florida.
He became a major and then a lieutenant colonel in the volunteer army.
Shortly after the First Battle of Manassas in July, he moved northward to Virginia to serve as aide-de-camp to Maj.
Gen. George B. McClellan.
He was promoted to the rank of major in January 1862.

Ingalls helped establish effective supply depots at Yorktown, Eltham's Landing, Cumberland Landing, and White House Landing for McClellan's Army of the Potomac during the Peninsula Campaign.
He skillfully evacuated White House Landing with all supplies, transportation and labor during the Seven Day's Battles.
Consequently, he became the Chief Quartermaster of the Army of the Potomac in August 1862 following the Peninsula Campaign and performed his duties efficiently during the Northern Virginia and subsequent Maryland Campaigns, winning praise for his logistics skills.

In June 1864, his old friend Ulysses S. Grant placed Ingalls in charge of supply with responsibility for all Federal armies operating against Petersburg and Richmond.
His logistics base at City Point, Virginia, became the largest port operation in the Western Hemisphere.

Ingalls won brevets to the rank of major general in both the regular and volunteer services.
With the outbreak of the Civil War in April 1861, Ingalls was reassigned to duty at Fort Pickens in Florida. He became a major and then a lieutenant colonel in the volunteer army. Shortly after the First Battle of Manassas in July, he moved northward to Virginia to serve as aide-de-camp to Maj. Gen. George B. McClellan. He was promoted to the rank of major in January 1862.
Ingalls helped establish effective supply depots at Yorktown, Eltham's Landing, Cumberland Landing, and White House Landing for McClellan's Army of the Potomac during the Peninsula Campaign. He skillfully evacuated White House Landing with all supplies, transportation and labor during the Seven Day's Battles. Consequently, he became the Chief Quartermaster of the Army of the Potomac in August 1862 following the Peninsula Campaign and performed his duties efficiently during the Northern Virginia and subsequent Maryland Campaigns, winning praise for his logistics skills.
In June 1864, his old friend Ulysses S. Grant placed Ingalls in charge of supply with responsibility for all Federal armies operating against Petersburg and Richmond. His logistics base at City Point, Virginia, became the largest port operation in the Western Hemisphere.
Ingalls won brevets to the rank of major general in both the regular and volunteer services.
Rufus Ingalls