USS Mount Baker (AE‑4), originally named USS Kilauea (AE-4), was acquired by the Navy 14 November 1940 while building by Tampa Shipbuilding Co., Tampa, Fla., as SS Surprise; delivered to Alabama Drydock & Shipbuilding Co., for conversion to Type C2; and commissioned 16 May 1941.

Type C2 ships were designed by the United States Maritime Commission (MARCOM) in 1937–38. They were all-purpose cargo ships with five holds, and U.S. shipyards built 328 of them from 1939 to 1945. Compared to ships built before 1939, the C2s were remarkable for their speed and fuel economy. Their design speed was 15.5 knots (28.7 km/h), but some could make 19 knots (35 km/h) on occasion. The first C2s were 459 feet (140 m) long, 63 feet (19 m) broad, and 40 feet (12 m) deep, with a 25-foot (8 m) draft. Later ships varied somewhat in size. Some, intended for specific trade routes, were built with significant modifications in length and capacity.