

They put it down the existing rail RoW that the highway was built around.
That station specifically connects with a major bus route that, in one direction, takes you to Midway Airport, and in the other, takes you to the University of Chicago campus, the Museum of Science and Industry, the new Obama center, and the DuSable Museum of African-American history, along with a handful of other museums, galleries, schools, and other amenities.

The Garfield Red Line station is well inside the city.