Why did western farmers make whiskey rather than sell their grain in eastern markets?

This is a misconception. Western farmers did sell their grain in eastern markets. In the 19th century, the Erie Canal and then the railroads made it possible to transport grain cheaply and efficiently from the Midwest to the East Coast. As a result, western farmers were able to sell their grain for a profit in eastern markets. However, some farmers did choose to make whiskey rather than sell their grain because whiskey was more compact and easier to transport than grain. Additionally, whiskey could be stored for longer periods of time than grain, which made it a more attractive option for farmers who lived in remote areas.