This study was an examination of businesses that became big businesses in the United States during the time period between the years of 1861 and 1890, a period of time frequently referred to as the “big business era.” The purpose of the study was to identify actions taken by businesses that enabled them to become and remain big businesses. A secondary purpose of the study was to show that these actions were explained by theories of Karl Marx and Max Weber. The results of the study showed that businesses which took specific actions were able to become and remain big businesses and these actions were explained by the theories of Marx and Weber. The results of the study demonstrate the ability of classical sociological theory to explain macro-level social change.