She was the third ship to be named for Commodore John Downes The Knox-class design was derived from the Brooke-class frigate modified to extend range and without a long-range missile system.

The Knox class had a range of 4,500 nautical miles (8,300 km; 5,200 mi) at a speed of 20 knots (37 km/h; 23 mph).

The ships were equipped with a torpedo-carrying DASH drone helicopter; its telescoping hangar and landing pad were positioned amidships aft of the mack.

The ship was commissioned 28 August 1971 Downes performed Anti-Submarine Warfare operations as a part of Destroyer Squadron 31, escort duty and naval diplomacy support, when necessary, for the Pacific Fleet.

During RIMPAC 89, the ship rescued one of two crew members washed overboard due to heavy seas.