USS Alert was a 90 long tons (91 t) steamship named A. C. Powell purchased by the Union Navy during the first year of the American Civil War.

For instance, on 12 November 1862, Captain Thomas Turner, the senior Union naval officer in the Hampton Roads-Norfolk area, warned Alert that .

the officers and men to be constantly on the watch ..." was especially important since Alert often served as tender to Philadelphia, the flag steamer of Acting Rear Admiral Samuel Phillips Lee who commanded the Union squadron.

In mid January 1863, Major General John Adams Dix notified Admiral Lee that there were "... indications of activity on the part of the enemy .

Since a major Confederate movement in that vicinity could jeopardize the entire Union hold on the south bank of the James, Admiral Lee ordered Alert and her sister warships to ready themselves to help turn back the Southern thrust should it come.

Longstreet, apparently hoping to improve the South's strategic position while finding food for General Lee's soldiers, headed for Suffolk.

When the Union Army called on the Navy for help, Admiral Lee ordered Lieutenant William B.Cushing to lead a group of gunboats up the Nansemond River – a tributary of the James – to assist Major General John J. Peck's troops as they tried to stop Longstreet's advance.

Because of her light draft, she moved above the bar of the river into the narrower, shallower, and more dangerous part of the stream near Suffolk where the fighting was fiercest.

Her work on the James reached its climax early in April when she participated in the naval expedition to Richmond, which took President Lincoln to the former Confederate capital.