The first three photos appear to be on what is now called the "Red Line" but was long known as "Howard Service" from downtown (where it is the State Street Subway) up to Dempster on the North Side. The last two pictures are of the northward turn across the Chicago River on the "Brown Line" that used to be called "Ravenswood Service" from the Loop downtown northwest up to Kimbal and Lawrence Avenues. Lake Street Service is a straight shot downtown to the Loop, but the Ravenswood Service joined the Howard Service where four tracks ran north until the Ravenwood split off and zigzagged a bit as it headed to Lawrence Avenue. The Merchandise Mart, once famous as "the world's biggest building" in 1930 when it was built because it held nearly 4 million square feet of floor space, was once the headquarters of the Chicago Transit Authority. Your friend lived close to the "Pink Line," formerly known as "Douglas Service." Sportsman's Park was a race track that was not far from the Cicero station on the Douglas Service Line.
When I was in college I worked summers as a ticket agent on those CTA lines. I remember rush hour downtown collecting over $6,000 in $0.25 fares in a mere 3 hours--and about a third of the customers used transers I punched, so they didn't contribute at all to that monetary total! While in grad school and when I was teaching in Chicago I spent summers driving CTA buses from trolleys to propane-powered to diesels.
