Final answer:
The true statement according to the historical data on U.S. urbanization is that the rural and urban populations were roughly equal in 1920.
Step-by-step explanation:
Among the provided statements and considering the historical trends and data from the U.S. Census Bureau, the accurate statement is C) Rural and urban populations in the United States were roughly equal in 1920. Based on the information, by 1900 about 40% of the U.S. population lived in urban areas, with this number reaching approximately 50% by 1920. The rural-to-urban shift has been significant, and by today's standards, about 80% of the U.S. population lives in metropolitan areas. Therefore, statement A is incorrect as a majority of the population lived in rural areas by 1900, and D is incorrect due to manufacturing and urban activities attracting more people to cities post-1940, leading to a decrease in the rural population, not an increase.