Burn down your cities and leave your farms, 

And your cities will grow up again.

But destroy your farms and grass will grow in every city. 

-William Jennings Bryan

  This demonstrates how much cities depend upon farms to produce their food. So many people don't know how to grow their own food. Before tractors and all the modern equipment, farmers grew food for themselves and had only a little extra to sell. Now we can grow much more food than we need. We have more cities than we used to because of this. But even so, without the farmers the cities would die out.