What did american colonists use windmills for

At sawmills, they used windmills to grind grain, pump water and cut wood.

Explanation:

The American colonists used the power generated by windmills at the sawmills to make the work eaiser and faster (and didn't need to use manpower or horsepower). The windmills power ground the grain between stones, pumped the water into the mills and could even cut wood.