Farming will provide your hungry citizens with more than pitchforks and torches.
In Era II of the Science Tech Tree, the "Plantation" research project adds new crops (Cannabis, Grape, Cocoa and Cotton) which become available but only on Farm control panels for Farms in provinces known for superb production of those plants (denoted by the symbol on some provinces seen on the World View map).
To create a farm, find the most fertile ground you can using the overlay system in the top left of the user interface. Then, select Farm from your toolbelt and click-and-drag to create your farm. Farms have a drop-down box to select what crop you would like them to grow next.