The B-24 was designed by a company called Consolidated Air. Originally a seaplane manufacturer, Consolidated developed the B-24 to meet some stringent requirements set by the Army Air Corps. Range, payload, and flight characteristics were to be much greater than previous bombers. Consolidated did not have a large enough facility in California to fully produce the planes, so wings were attached in their parking lot. Since the wingspan is made of two pieces, that part of the plane doesn’t have the same structural strength as a mono wing bomber, like the B-17. That’s one reason why the B-17 has the reputation for durability, while the B-24 is known more for range and lifting capacity. With the wing on top of the fuselage instead of at the the bottom, the B-24 was perfect for long range sub patrols in the Atlantic, or bombing missions in the Pacific.
I heard one story once of a B-24 that lost all its engines over the English Channel. The extra lift provided by the high, narrow wing allowed the crew to glide all the way home to their aerodrome. It seems like a LONG way to glide given the operating ceiling of a B-24, but a remarkable example of the reputation this bomber had among the air crews.
Consolidated did not have facilities to test hull integrity, so they actually filled the completed hulls with water, and looked for leaks. Once it all dried out, they could install all the equipment. Without the sophisticated design teams used by Boeing, Consolidated produced a first rate bomber.