This book provides an excellent overview of a crop whose importance to the global economy has been quite understated. It reveals, for example, that as late as 1900 a full 1 percent of the world’s workforce was involved in the cultivation, harvest, and processing of cotton into textilies.

Incidentally, the book also demonstrates the value of urbanization and clustering of industry into particular geographic regions. It helped me to understand that the reason that port cities are so vibrant is not that any one specific thing can be obtained there, but that anything that is commercially available can be obtained there.

Port cities are also places of mixing. Want to combine Madagascar vanilla with South American cacao? You’re going to be able to do that better in San Francisco than you could in either of the points of origin for the raw materials. This is due to the connections (much cheaper to transport in bulk over sea than land), the financial capital, the human capital (immigration), and the ability to combine raw materials from disparate sources. This remains true today, with the caveat that airports can serve a similar role at smaller scales.

Access to a port also greatly increases your addressable market. If you make the best chocolate in the world from a factory in Idaho, good luck–you will need to appeal to extremely devoted fans. A product produced in a port city can become a global staple quite rapidly.

Note also that you don’t have to know a priori where these suppliers or markets will be. Unlike roads, the oceans are open to all. This is one reason that early institutions guaranteeing free and safe sea travel (such as the law of the sea and powerful European navies) were such important guarantors economic growth.