American Legion was a United States Navy ship first launched on 11 October 1919 and decommissioned on 20 March 1946. She was built for the United States Shipping Board (USSB), one of the planned World War I troop transports converted before construction into passenger and cargo vessels, the Emergency Fleet Corporation Design 1029 ships. The ship was laid down as Koda and perhaps assigned the name Badger State at one point, but renamed American Legion before launch and one of only a few of the design not taking a state nickname. Originally operated by the USSB's agents and the Munson Steamship Line the ship saw commercial service until laid up 13 March 1939.

American Legion was formally transferred to the War Department for use as a United States Army transport on 19 December 1939 operating as USAT American Legion until transfer to the United States Navy 22 August 1941. The Navy commissioned the ship USS American Legion initially classifying the ship a transport with hull number AP-35. On 1 February 1943 the Navy reclassified the ship as an attack transport () with hull number APA-17. American Legion decommissioned on 28 March 1946 and was sold for scrap 5 February 1948.

Construction American Legion was a steel-hulled, twin-screw passenger and cargo steamship, laid down as yard hull number 242 on 10 January 1919 under a United States Shipping Board (USSB) contract at Camden, New Jersey, by the New York Shipbuilding Corporation. The name was the result of efforts by William J. Brown, an Emergency Fleet Corporation inspector and member of the American Legion, who inspected the hull, proposed its name change to the Pennsylvania American Legion conference with passage of a resolution which was immediately publicized. A week from that publication the ship was launched as American Legion on 11 October 1919 with Emily Frelinghuysen, wife of New Jersey senator Joseph S. Frelinghuysen christening the ship. The ship, a type known in commercial service as "535's" for their length overall, was assigned the United States official number 221478.

The ship was one of three intended to become United States Army transports already under construction at the yard: hull 240 Wenatchee, hull 241 Sea Girt and hull 242 Koda. Of those one had been launched and a second was ready for launch when the USSB changed plans from troop transports to completion as passenger ships. At some point American Legion may have been assigned the name Badger State by USSB in conformance with the majority of the ships of the design but the three ships begun as Army transports when the design changed to passenger-cargo ships remained the only ones not formally assigned the state nicknames.McKellar only shows Koda and that name is shown along with two other ships, hull 240, Wenatchee (apparently initially C. M. Schwab) and hull 241, Sea Girt that was completed as Southern Cross, of the early New York Shipbuilding group of this type. Later references begin associating the name Badger State with the ship launched as American Legion and a few mention Badger State being the name at launch. The "State" names were assigned to new construction of this type intended from the start as commercial ships and Badger State may have been briefly assigned retroactively before efforts of the American Legion resulted in the name given for the organization. Contemporary sources make it clear the ship was launched as American Legion. A close look at the period shows proposed names existing only on paper in a number of cases. In any case, the ship was launched as American Legion, a name exceptionally kept throughout the ship's career, and was delivered to the USSB upon completion on 15 July 1921.

Before delivery American Legion and Sea Girt, soon to become Southern Cross, were modified for tropical service carrying about 300 first class passengers.

Commercial service

American Legion, flying the Munson Steamship Line's flag which had been allocated the ship for operation in fast passenger service to South American ports, left the Camden yards at five-thirty on the afternoon of 16 July 1921 for the one-day voyage to Hoboken, New Jersey with cabins filled with dignitaries. The line's founder and owner, Frank C. Munson, and his wife were hosts to a party composed of executives of New York Shipbuilding, USSB Commissioners, members of Congress and prominent members of the American Legion. Both National and regional officials of the American Legion had been guests at a dinner aboard prior to sailing and had passed a resolution expressing appreciation for the naming of the ship after the organization and resolved to present a plaque bearing the American Legion's emblem to the ship. The plaque, to hang in the ship's dining room, was presented in New York in 1922. At four-thirty on the afternoon of 17 July American Legion arrived at Pier 3, Hoboken. On 23 July 1921 the ship departed on her maiden voyage to South America.

American Legion, along with sister ship and the seized Norddeutscher Lloyd ships and allocated to Munson by the USSB after the war, began operating as the Pan America Line serving a New York-to-Rio de Janeiro, Montevideo, and Buenos Aires route with Santos, added during return voyages. On 31 August 1922, American Legion suffered a mishap in which she rammed several Argentine Navy ships; she split the despatch boats in two and sank her and damaged the despatch boats and , the survey ship , the troopship , and the gunboat .

By 1924 Aeolus and Huron had dropped off the New York-Rio de Janeiro-Montevideo-Buenos Aires route to be replaced by sister "535's" and . The addition of the relatively fast "535's" on the direct route between New York and South America resulted in the British Lamport and Holt Line cutting its first class rates to South America, from $415 to $315 New York-Rio de Janeiro fare, and the USSB then cutting its rates to $295 for the same route and offering a round trip to Rio de Janeiro at $450.

As the USSB sold off its vessels the Munson Steamship Line bought the four vessels operating for its Pan America Line service in February 1926. Each ship, including American Legion, was purchased for a price of $1,026,000. For the next fourteen years, American Legion and her running-mates were familiar sights on that particular passenger-and-cargo route. By 1931 American Legion and her sister "535's" had been taken off the South American service and were running between New York and Bermuda. Financial difficulties forced foreclosure of the Munson Steamship Line on 13 March 1939 and American Legion was then laid up in the Patuxent River.

Army troopship service Her enforced idleness did not last long. A little under three months after the German invasion of Poland, triggering World War II in Europe, the Maritime Commission (the successor to the USSB) transferred American Legion to the War Department on 28 November 1939 for use as a troop transport. On 19 December 1939, the ship was formally transferred, and taken to New York for rehabilitation and conversion by the Atlantic Basin Iron Works of Brooklyn, New York.

USAT American Legion departed New York City early in February 1940, on her maiden voyage, bound for Panama. Over the next few months, the ship made five round-trip voyages to the Canal Zone, with stops at Charleston, South Carolina, and San Juan, Puerto Rico, carrying civilian and military passengers. The worsening situation in Europe, though, soon resulted in the ship's receiving a special mission.

Vital mission to Petsamo President Franklin D. Roosevelt directed that American Legion leave New York immediately and proceed to Petsamo in northern Finland. There, she was to embark the Crown Princess Märtha of Norway and her party and bring them to the United States, their homeland having fallen to the Germans the previous spring. Further, as Acting Secretary of State Sumner Welles reported to the United States Minister in Sweden, the President also desired that Mrs. J. Borden Harriman, the former American Minister to Norway, return in the same vessel. The transport would "likewise bring back to this country such Americans in Scandinavian countries as can be accommodated and as may not be able to return safely in any other way."

American Legion — her neutrality shown clearly by the U.S. flags painted prominently on her sides — sailed for Finland on 25 July, and reached Petsamo on 6 August, as scheduled. On the 15th, she embarked Crown Princess Märtha, and her three children, the Princesses Ragnhild and Astrid, and Prince Harald. The Army troopship also embarked a host of American nationals and refugees from a variety of countries: Poland, Finland, Estonia, Latvia, Lithuania, Sweden, Norway, Denmark, Germany, and the Netherlands, the total number of people being 897. Among the passengers was a young Danish comedian and musician, Victor Borge. The American Legation in Stockholm, Sweden, also consented to the embarkation of 15 "prominent nationals of American republics...including the Mexican minister..."

Unbeknownst to probably all but a handful of individuals, American Legion also took on board an important cargo during her brief stay at Petsamo. Before she sailed on the 16th, after an almost Herculean effort involving taking this special cargo by truck the entire length of Sweden, the transport loaded a twin-mount 40-millimeter Bofors antiaircraft gun, "equipped with standard sight, and accompanied by spare parts and 3,000 rounds of ammunition." The State Department had obtained the cooperation of no less than three governments to make possible the shipment of the Bofors gun: British, Swedish, and Finnish. The move had been made none too soon, for American Legion was the last neutral ship permitted to leave Petsamo.

American Legion sailed for the United States on 16 August, and reached New York, 12 days later, escorted the final leg of the voyage by several American destroyers. The transport unloaded the Bofors brought from Petsamo, whence it was shipped to Dahlgren, Virginia, where it would be tested, and ultimately adopted by the US Navy and produced domestically. Its installation in American warships from late 1942 proved a significant upgrading to the antiaircraft capability of the ships of the US Navy.

Other transport missions American Legion soon returned to the more prosaic calling she had pursued since earlier in the year, that of an Army transport, and resumed the regularly scheduled service between New York and the Panama Canal Zone. Ultimately, as the United States expanded her defense perimeter, American Legion supported this movement, transporting men and cargo to such ports as Hamilton, Bermuda, and Port-of-Spain, Trinidad, as well as to Cristóbal, in the Canal Zone.

As the United States began assuming a greater share of the Battle of the Atlantic, to aid the hard-pressed British, the 6th Marine Regiment was taken to Iceland, where it relieved a British garrison of defense duties. A second troop and supply movement followed. American Legion from New York on 27 July 1941, as part of a convoy which included within its escort the aircraft carrier .

American Legion — whose cargo included Army Air Corps gear earmarked for use by the 33rd Pursuit Squadron (whose Curtiss P-40 fighters were flown off from Wasp) — reached Reykjavík, Iceland, on 6 August. Unable to enter the inner harbor because of her deep draft, American Legion discharged her cargo and disembarked her passengers into tank lighters and motor launches over the days that followed, the cargo movement facilitated by marines and sailors from the ships.

Navy commission Having delivered the men and goods to Reykjavik, the convoy sailed on the 12th with its heavy escort and reached New York on 21 August. The next day, American Legion was acquired by the Navy and classified as a transport, AP-35. She was placed in commission on the afternoon of 26 August 1941.