The real lineage of the Harvard began in 1937 with a USAAF competition to develop a basic trainer. The requirements were for a type capable of basic instruction as well as simulating the controls and feel of an actual combat aircraft. It also had to be able to carry guns and bombs as necessary.

North American's new design was based on their NA-16, but was vastly improved. It incorporated the Wasp engine, A Hamilton Standard variable pitch prop, a hydraulic system to power the flaps and the new inward-folding retractable landing gear. Later a stressed skin fuselage, a new rudder and angular wingtips were added. This prototype (called the NA-26) won the competition. It went into production as the BC-1. (BC for "basic trainer")

The Royal Air Force initially ordered several hundred of this variant, with British instruments and radios, in 1938. The Brits coined the name "HARVARD" for it. (by which name it would become known in all the commonwealth countries....except for Australia, where it was called the "WIRRAWAY") This version retroactively became known as the MK I.

In 1940, the USAAF changed the designation to AT or advanced trainer, so the American machine became the AT-6. The U.S. Navy version was called the SNJ.

Even with their huge new 2,000,000 square foot plant, North American couldn't keep up with the wartime demand  so a new factory was built in Dallas, leading, after 1942 to the AT-6 being called the "TEXAN".

Beginning in January, 1940 The HARVARD MkIIB version was built under license by NOORDYN of Montreal, Canada for the Royal Canadian Air Force, the RAF and the USAAF. Ultimately 2,557 Harvards were built here.

After the war the MK IV version was built by CANADIAN CAR AND FOUNDRY. All in all, some 21,342 aircraft of the NA-16 series were built.