After shakedown in the Caribbean, Rowan departed Norfolk on 17 May 1940 for duty in the Pacific, based at San Diego, California.

In May the limits of the Neutrality Patrol were extended and the Navy gradually expanded its responsibilities for protecting transatlantic convoys.

Then, in early November, she was ordered to escort Convoy WS-12X, carrying British reinforcements for the Near and Far East, from Halifax, Nova Scotia to Cape Town.

Sailing from Halifax on 10 November, she reached Cape Town on 9 December, 2 days after the United States entered World War II.

In January 1942, she returned to the east coast of the United States and resumed convoy duty in the North Atlantic and the Caribbean.

Upon departing the convoy on 10 May, she proceeded to Hvalfjorður, Iceland, and on the 11th joined TF 99, which was acting as a part of the British Home Fleet based at Hvalfjordur and Scapa Flow.

On the 29th, TF 99 put into Scapa Flow and on 12 June got underway to return to Iceland and repeat its previous mission for convoys PQ 17 and QP-13.

That convoy, shadowed by German reconnaissance planes despite heavy fog, had already lost two freighters; one grounded, the other damaged by ice and ordered back.

Shortly thereafter, the convoy was ordered scattered and the escorts sent to support the cruisers in an anticipated engagement with German heavy units which were rumored to have left the fjords of Norway.

In September, she trained and conducted patrols out of Norfolk, Virginia, and Portland, Maine; then, in October joined TF 34 for Operation Torch, the invasion of North Africa.

On the 10th, she patrolled off Casablanca and participated in action against Vichy ships attempting to turn back the invasion.

On the 26th she added shore bombardment, against enemy positions between Cefalù and Stefano di Camastra, and into August she supported the "leap frog" landings along the coast.

This article incorporates text from the public domain Dictionary of American Naval Fighting Ships.