[2][9] The Worthington Pump & Machine Corporation of Harrison, New Jersey, built John W. Brown's vertical triple expansion steam engine, which cost $100,000.

[10][11] After ten more days of post-delivery work in Baltimore to prepare her to get underway, John W. Brown departed on 29 September 1942 to steam down the Chesapeake Bay to Norfolk, Virginia, where she underwent degaussing and deperming to make her less likely to trigger magnetic sea mines.

Getting back underway, she steamed alone north through the western Indian Ocean off the east coast of Africa, and anchored in the Persian Gulf on 25 December 1942, two and a half months after leaving New York.

[10][11][13] Ports in the Persian Gulf were overwhelmed by the amount of cargo arriving from Allied countries, and so John W. Brown was forced to lie at anchor for a month until she could begin to unload at Abadan, Iran, where she dropped off the two P-40s and some of the tanks in late January 1943.

[3] After returning to the United States, she became the first of 220 Liberty ships to undergo conversion into a "Limited Capacity Troopship" capable of transporting up to 450,[2] 550,[3] or 650[4] (sources vary) troops or prisoners-of-war.

After taking aboard 241 American and Free French troops, 261 tank destroyers, trucks, and cars, and a load of asphalt there, she departed in convoy on 30 November and arrived at Naples on 7 December 1943.

On 27 December, the Liberty ship SS Zebulon Pike rode over John W. Brown's anchor cable and collided with her starboard side, causing significant damage.

The following day, the German submarine U-969 attacked the convoy, and the Liberty ships SS Peter Skene Ogden, only 500 yards (457 m) ahead of her, and SS George Cleeve, only 850 yards (777 m) off her starboard bow, suffered torpedo hits causing such severe damage that both ships had to beach themselves and became total losses, but John W. Brown was left unharmed.

[18] On 23 March 1944, John W. Brown steamed up the Hudson River to Yonkers, New York, where she entered Blair Shipyard for repairs to the damage suffered during the collision with Zebulon Pike and to have two more 3-inch 50-caliber guns and quarters for additional United States Navy Armed Guard personnel to man them.

[19] Her repairs and alterations complete, John W. Brown steamed to Brooklyn, where on 3 April 1944 she began to load a cargo of high explosives.

[19] John W. Brown spent the next five weeks at anchor at Naples during preparations for Operation Dragoon, the Allied invasion of southern France.

Although fully loaded with cargo, 15 U.S. Army officers, and 299 U.S. Army enlisted men by 29 July 1944, she remained at anchor until 13 August, when she finally got underway for the invasion,[19] passing as she left Naples a British destroyer from which British Prime Minister Winston Churchill was flashing his "V for Victory" sign at the passing ships.

[21] John W. Brown got underway from Baltimore on 19 October 1944 for her fifth voyage and proceeded to Hampton Roads, where she joined a convoy for a transatlantic passage.

Carrying 356 passengers – including 30 United States Army Air Forces fighter pilots and troops of the all-African American 758th Tank Battalion – she departed Hampton Roads in convoy on 22 October 1944.

The convoy encountered very bad weather during its trip but did not come under enemy attack, and John W. Brown arrived at Augusta safely on 14 November 1944.

Braving high winds and enormous waves but encountering no enemy forces, her convoy arrived safely at New York on 29 December 1944.

She embarked 54 U.S. Army passengers at Newport News and departed on 23 January in convoy for Naples, at first facing heavy weather but otherwise making an uneventful transatlantic crossing.

[23] John W. Brown was taken under repair by Atlantic Basin Iron Works in Brooklyn from 7 to 11 April to have her balky boiler fixed and have a gyrocompass installed.

[23] On 23 April 1945, John W. Brown left in convoy with a load of U.S. Army general cargo below and trucks lashed to her decks to begin her seventh voyage.

The convoy encountered bad weather but no enemy forces while crossing the North Atlantic and arrived off The Downs on the southeast coast of England on V-E Day, 8 May 1945.

[24] During her career, John W. Brown had carried nearly 10,000 troops, including the two shiploads of German prisoners-of-war that she transported from North Africa to the United States.

After unloading the coal, she embarked ten civilian airline pilots – nine men and one woman – under United States Government contract to fly planes to Denmark.

After she unloaded her cargo, John W. Brown's final voyage officially was completed on 19 November 1946, bringing her seagoing career to an end.

[3][20][26][27][28] Training aboard John W. Brown began in December 1946, many of the early students being men who had dropped out of classes at the Metropolitan Vocational High School during World War II to serve as merchant mariners or in the U.S. Navy or U.S. Coast Guard.

Students studied standard academic subjects and took boat building, marine radio, marine electrician, and maritime business classes in the high school's main building ashore; aboard John W. Brown they learned their seafaring trade, either as deck hands, engine room personnel, or stewards, and they also performed all maintenance and repairs the ship required.

New York City officials gave thought to ending the maritime vocational training program and closing the school, but cost-cutting measures were instituted, such as returning in September 1957 to the schedule of having students study in the school's building for a week at time and aboard ship for a week at time, eliminating the expense of busing.

[28] However, continuing budget problems finally led to the school closing in mid-1982, and John W. Brown remained idle in New York Harbor for the next year.

It did not succeed in finding her a berth in New York, and instead she was towed to the James River Reserve Fleet near Norfolk, Virginia,[2] in July 1983 with her future in doubt.

[29] Four weeks later, on 21 September 1991, two days after the 49th anniversary of her completion, John W. Brown carried about 600 members and guests on her "matron voyage", her inaugural cruise.

In addition to her floating museum role, John W. Brown still gets underway several times a year for six-hour "Living History Cruises" that take the ship through Baltimore Harbor, down the Patapsco River, and into the Chesapeake Bay.