From the outbreak of the Civil War, the Lincoln Administration seemed to feel that the British Government's sympathies lay with the Confederacy.

To prepare for such an eventuality, the Federal Navy Department embarked upon a program of developing very fast seagoing steamships capable of overtaking all ships they might pursue and of escaping from any they might wish to elude.

These engines were not ready when Ammonoosuc was launched and the collapse of the Confederacy prompted a significant slowdown on the work as that all but eliminated the Navy's need for fast, new warships.

By late in the spring of 1868, the ship was finally ready to go to sea under her own power and departed New York City on 15 June for a run to Boston, Massachusetts at full speed.

Dense fog over much of her course prevented her from proceeding at top velocity during most of the passage, but during one three-hour period she averaged 17.11 knots while moving from Cape Cod to Fort Warren, the highest sustained speed ever attained by a ship up to that time.