From Domestic Cookery (1869) by Elizabeth Ellicott Lea: Pictured is a tall, narrow, wooden cask/barrel with a manually operated churn. Before it was used it would be filled with water to cool the churn and swell the barrel. In the 18th century butter became a standard part of the American diet. It was usually made at home in wooden or stoneware churns. Churning butter was an arduous process requiring time and stamina. Cream was poured into the cask and agitates with the churn (or dasher) until particles of butter float to the surface. The butter was then removed, washed, and then worked into a wooden bowl with a wooden paddle to remove excess moisture. What remained in the cask was butter milk. (Real buttermilk is churned, not cultured). Salt was added to the butter which flavored and preserved the butter. Sometimes carrot juice was also added in order to add color (especially in the winter when the cream is very light in color). The resulting butter was kept in stone crocks or wooden boxes.
