The Mill is a building in Age of Empires III that is used to attain a steady source of food, but does not provide as much of the resource per Settler as hunting unless a significant effort is made in normal upgrades, Home City Cards, and native upgrades. Up to 10 Settlers can work on a Mill at once, though due to collisions between units it is best to only use 7 per structure. Mills placed too closely together (side by side with no space between them) may cause some Villagers to "migrate" to the adjacent Mill; this bug occurs with Plantations and Rice Paddies as well. Also, there are some upgrades that the Mill provides for faster farming.
The Mill is comparable to the Plantation, which works the same way, but produces coin. Mills also replaces the role of Farms in earlier games in the series. However, Farms are reintroduced in The WarChiefs, they act as the Native American version of the Mill and Livestock Pen.
"A mill is used to break grains down into smaller pieces making cooking and baking easier. They were historically powered by wind, water, or livestock. Grain is ground between stones, known as millstones, until it is fine enough to be used for whatever purpose is needed. Flour for bread was made in this manner."