These ships were of the basic C-3 design with accommodations for about 150 passengers each.  The plan called for their operation with the Brazil, Uruguay and Argentina.  They were of 17,600 displacement tons, 492 feet long, 69 feet beam.  Each ship was blessed before launching; this was said to be the first instance of its kind in modern times.  The Rio ships were destined never to enter the passenger service.  They were requisitioned by the Navy on May 20, 1941, and converted to baby flattops for the British Royal Navy (3) and the US Navy (1).

Launched November 27, 1940, the Rio Hudson was the first of four additional ships, referred to as the "Rio" ships.  Madame Alzira Vargas Peixoto, daughter of the president of Brasil, sponsored the ship.  She was renamed by the Royal Navy as the HMS Avenger.

Launched December 18, 1940 (see additional information to the right).  In May 1942 she was transferred from the United States Navy to the Royal Navy as the HMS Biter.  During WWII she was damaged by a torpedo from her own aircraft and then later damaged by fire while in port.  She was returned to the United States Navy in April 1945 and then immediately transferred to France as the Dixmude.  In June 1966 she was returned to the United States Navy for disposal and was later sunk as a target.

Launched March 1, 1941, the Rio de la Plata was the third "Rio" class ship.  She was renamed by the Navy as the USS Charger (CVE-30).

Launched April 12, 1941, the Rio de Janeiro was a passenger cargo liner built for Moore-McCormack Lines by the U.S. Maritime Commission.  (See above for more information.)  Her sponsor was Madame Felipe Espil (b.1899 d.1995), writer and wife of the Argentine Ambassador to the United States.  Once WWII began, the Rio de Janeiro was transferred to the Royal Navy as the HMS Dasher and put into military service never to return to Moore-McCormack.  She was put into service as a convoy escort, but was sunk by explosion during aircraft refueling on March 27, 1943.