With her home port at Seattle, Washington, McArthur spent her career operating along the United States West Coast, in Alaskan waters, and in the eastern Pacific Ocean.

She also conducted Chase Encirclement Stress Studies (CHESS) -- marine mammal surveys throughout the eastern tropical Pacific—and took part in the Oregon, California, Washington (ORCAWALE) Project in support of protected species research efforts; she also participated in the Sustainable Seas Expedition.

On 26 October 1969, McArthur was docked in Ketchikan, Alaska, when a gunman shot a member of her crew, wiper John Fleagle, in the back on the pier.

Fleagle managed to get aboard the ship and entered the stateroom of ESSA Corps Lieutenant, junior grade, Robert C. Husted, Jr., at approximately 06:00 hours.

Blackwater Worldwide described McArthur as a multipurpose maritime vessel designed to support military and law enforcement training, peacekeeping, and stability operations around the world.

They are supposed to be advocates for American businesses, but this was Blackwater, a company that Secretary of State Hillary Clinton had proposed banning from war zones when she was a presidential candidate.According to Wired magazine, civil suits from McArthur's civilian crew members caused cancellation of plans to employ her on military missions;[8][9] three civilian crew members filed harassment suits.