@cptofthehouse - for low income students in particular, college enrollment has been surging. As there is also a greater number of low SES in our urban centers than in rural America (heck, there are more PEOPLE as well), it’s quite likely most of these gains are coming from there.
https://www.census.gov/library/stories/2017/11/income-poverty-rural-america.html
@Marlowe1 has mentioned upthread UChicago’s history of attracting certain students from the small towns and rural communities of America. It’s a wide geographical area. As for attributes, UChicago is more likely to see the cream of the crop than the typical high schooler (by the way, that was also true at my son’s urban high school. Most simply aren’t interested in the school for a variety of reasons). There have always been smart, hardworking kids from Small Town America - that they leave and don’t return is the biggest challenge facing those communities.