Why is Boston called Beantown?
The simplest and most straightforward answer to this question is because of Boston baked beans, of course! Now if the question were why does Boston love baked beans so much, the answer gets a little more complicated.
If I had to give a single word answer, I would have to say mercantilism. This was the colonial economic period where the ‘triangle trade, reigned. This was, in fact, a triangle of trade routes, from the Carribbean where slaves from West Africa grew sugar, which was supplied to New England or all the way to the Old World to be distilled into rum, which was then used to purchase more slaves from West Africa, to be shipped to the Americas to grow more sugar. Of course, the full trade was much more complicated than that, using many different goods in various overlapping triangles. Why did the triangles overlap? This is because currents and trade winds (created from the Coriolis effect of physics and weather) made it much easier to sail in a clockwise motion (in the Northern Hemisphere) than to try to sail in the opposite direction. Thus, the triangle went from Europe, to West Africa, to the Americas (specifically, the Carribbean then to New England) and back to Europe. So direct import of molasses from Europe was quite difficult and expensive, even though it was quite available. However, it was very easy to ship molasses and sugar from the Carribbean up to New England, including the city of Boston.
Boston had an extreme excess of beans, because they were cheap and easy to grow in such awful soil and climate conditions, and provided lots of nutritional value. Molasses from the Carribbean slaves made an excellent dish when mixed with navy beans and baked; making the famous dish of Boston baked beans.