In March 1939, the United States Army Air Corps issued Circular Proposal 39-640, a specification for a twin-engined medium bomber with a maximum speed of 350 mph (560 km/h), a range of 3,000 mi (4,800 km) and a bomb load of 2,000 lb (910 kg).
On 5 July 1939, the Glenn L. Martin Company submitted its design, produced by a team led by Peyton M. Magruder, to meet the requirement, the Martin Model 179.
Martin's design was evaluated as superior to the other proposals and was awarded a contract for 201 aircraft, to be designated B-26.
The B-26 went from paper concept to an operational bomber in approximately two years.
Additional orders for a further 930 B-26s followed in September 1940, still prior to the first flight of the type.

The B-26 was a shoulder-winged monoplane of all-metal construction, fitted with a tricycle landing gear.
It had a streamlined, circular section fuselage housing the crew, consisting of a bombardier in the nose, armed with a .30 in (7.62 mm) machine gun, a pilot and co-pilot sitting side by side, with positions for the radio operator and navigator behind the pilots.
A gunner manned a dorsal turret armed with two .50 in (12.7 mm) machine guns (the first powered dorsal turret to be fitted to a U.S. bomber), and an additional .30 in (7.62 mm) machine gun was fitted in the tail.

Two bomb bays were fitted mid-fuselage, capable of carrying 5,800 lb (2,600 kg) of bombs, although in practice such a bomb load reduced range too much, and the aft bomb bay was usually fitted with additional fuel tanks instead of bombs.
The aircraft was powered by two Pratt & Whitney R-2800 Double Wasp radial engines in nacelles slung under the wing, driving four-bladed propellers.
The engines were manufactured at the Ford Dearborn Engine plant in Dearborn, Michigan, USA.
The wings were of low aspect ratio and relatively small in area for an aircraft of its weight, giving the required high performance, but also resulting in a wing loading of 53 lb/sq ft (260 kg/m²) for the initial versions, which at the time was the highest of any aircraft accepted for service by the Army Air Corps, until the introduction of the  Boeing B-29 Superfortress, with the then-astonishing wing loading of 69.12 lb/sq ft (337.5 kg/m²) (although both would be considered lightly loaded by the standard of combat aircraft of the next decade).

The first B-26, with Martin test pilot William K. "Ken" Ebel at the controls, flew on 25 November 1940 and was effectively the prototype.
Deliveries to the U.S. Army Air Corps began in February 1941 with the second aircraft, 40-1362.
In March 1941, the Army Air Corps started Accelerated Service Testing of the B-26 at Patterson Field, near Dayton, Ohio.
In March 1939, the United States Army Air Corps issued Circular Proposal 39-640, a specification for a twin-engined medium bomber with a maximum speed of 350 mph (560 km/h), a range of 3,000 mi (4,800 km) and a bomb load of 2,000 lb (910 kg). On 5 July 1939, the Glenn L. Martin Company submitted its design, produced by a team led by Peyton M. Magruder, to meet the requirement, the Martin Model 179. Martin's design was evaluated as superior to the other proposals and was awarded a contract for 201 aircraft, to be designated B-26. The B-26 went from paper concept to an operational bomber in approximately two years. Additional orders for a further 930 B-26s followed in September 1940, still prior to the first flight of the type.
The B-26 was a shoulder-winged monoplane of all-metal construction, fitted with a tricycle landing gear. It had a streamlined, circular section fuselage housing the crew, consisting of a bombardier in the nose, armed with a .30 in (7.62 mm) machine gun, a pilot and co-pilot sitting side by side, with positions for the radio operator and navigator behind the pilots. A gunner manned a dorsal turret armed with two .50 in (12.7 mm) machine guns (the first powered dorsal turret to be fitted to a U.S. bomber), and an additional .30 in (7.62 mm) machine gun was fitted in the tail.
Two bomb bays were fitted mid-fuselage, capable of carrying 5,800 lb (2,600 kg) of bombs, although in practice such a bomb load reduced range too much, and the aft bomb bay was usually fitted with additional fuel tanks instead of bombs. The aircraft was powered by two Pratt & Whitney R-2800 Double Wasp radial engines in nacelles slung under the wing, driving four-bladed propellers. The engines were manufactured at the Ford Dearborn Engine plant in Dearborn, Michigan, USA. The wings were of low aspect ratio and relatively small in area for an aircraft of its weight, giving the required high performance, but also resulting in a wing loading of 53 lb/sq ft (260 kg/m²) for the initial versions, which at the time was the highest of any aircraft accepted for service by the Army Air Corps, until the introduction of the  Boeing B-29 Superfortress, with the then-astonishing wing loading of 69.12 lb/sq ft (337.5 kg/m²) (although both would be considered lightly loaded by the standard of combat aircraft of the next decade).
The first B-26, with Martin test pilot William K. "Ken" Ebel at the controls, flew on 25 November 1940 and was effectively the prototype. Deliveries to the U.S. Army Air Corps began in February 1941 with the second aircraft, 40-1362. In March 1941, the Army Air Corps started Accelerated Service Testing of the B-26 at Patterson Field, near Dayton, Ohio.
Martin B-26 Marauder