Rural vs. Urban
The main reason a larger fraction of the population lives in urban areas now than in 1910 has more to do with how we define urban than anything else. In 1910, any area outside of a major city was considered rural. Some areas inside the cities themselves were considered rural. There were no "suburbs". The inner and outer rings of our metropolitan statistical areas were rural. If you take this into consideration, the truth is that an actual number and the fraction of people living in areas previously designated as rural has actually increased. The actual number and fraction of people living in the cities has either decreased or remained stable. When you change the designation of a geographic area, it does not necessarily mean more people are now city dwellers. There are more people living in the heartland of America than ever, even if you only count 16% of the population as being there. Right now typing this I am 60 miles from three major US cities and I am surrounded by farmland and this area is not considered rural.
