McLanahan was laid down 29 May 1941 by the Bethlehem Shipbuilding, San Pedro, California; launched 2 September 1942; sponsored by Mrs. Dorothy W. Howard; and commissioned 19 December 1942.

On 19 December 1943, a first birthday celebration was held for McLanahan in the Grand Ballroom of the St. George Hotel, Brooklyn, N.Y.[1] On 13 May 1944, she departed Oran for Naples to aid in the Anzio offensive.

McLanahan returned to the Mediterranean 21 December and on 19 January 1945 joined "le Grande Garde" patrol in the bombardment of the Ligurian coast from Monte Carlo to Genoa.

She returned to Toulon 21 March for an awards ceremony at which Rear Admiral P. Jaugard, French Navy, presented her captain, medical officer, and 12 other crewmembers with the Croix de Guerre.

On 14 August, McLanahan departed Boston, Massachusetts for the Pacific war zone, but, with receipt of news of Japan's surrender, her orders were changed.

She remained with the Atlantic Fleet, completing cruises to New York, New Orleans, Louisiana and Guantanamo Bay before mooring at Charleston, South Carolina, 3 November.