Why does the Boeing 747 have its characteristic hump?

I am currently reading an amazing book about the development process of the world's first wide body, twin aisle aircraft, Boeing's 747. The book titled '747' is written by Joe Sutter, the chief engineer in charge of the project. The Jumbo Jet is truly an amazing piece of engineering, even more so when you appreciate that the first one flew almost half a century ago in 1969 and the latest version the 747-8i is holding its own rather well, well into the 21st century. Well enough in fact, that premier airlines like Lufthansa are ordering new ones even today.

Here's a question I have always had about the jumbo jet. Why does it have the characteristic hump at the fore end of the fuselage? Why was it designed that way?

When Boeing started development of the 747 in 1965, the company did not have confirmed orders for their 350 passenger behemoth, only expression of interest from Pan-American airlines. Joe Sutter and his team realized that air cargo was going to be a huge market and their new aircraft would be big enough to carry standard truck sized cargo containers 8 feet wide by 8 feet tall and 20 feet long. In fact it could carry two of them side by side on its main deck. The problem was, they needed to figure out a way to get these into the aircraft, and the method that allowed the fastest loading and unloading was through the nose of the aircraft. They designed a loading door into the nose of the aircraft that hinged upwards. The engineers then had to move the flight deck, i.e. the cockpit, above the hinges and therefore above the main deck. The hump behind the cockpit was gently sloping for aerodynamic reasons. Over time, on succeeding generations of the 747, Boeing has been extending the upper deck aft to the point that on the 747-400, the Stretched Upper Deck can carry 40 passengers in Business Class configuration or 56 in Economy.

One of the most recognizable shapes in aviation owes its design to a team of engineers building in some insurance against the possibility of obtaining insufficient passenger jet orders. A good thing too, for the jumbo jet went on to become a runaway success in the air cargo world, so much so, that half of all air freigther cargo in the world is carried by 747s.

So now you know.