The Chicago South Shore & South Bend Railroad, probably street running here in Michigan City, IN. Still running today as the South Shore Line it serves commuters from northern Indiana going to Chicago for work, shopping and the sights and sounds of the big city.
Googling "Pappy's Pram" I found out they are arial photographers, so, most likely they're holding high altitude cameras.
When my dad was in the Marine Corps in the late '50s and early '60s, they were issued the Mighty Mite. The Marines considered them a piece of shit and hated them. They are very rare today, as Marines pushed most of them over cliffs or otherwise intentionally destroyed them.
The South Shore used to run right down Chicago Ave in East Chicago also. This photo shows the train stopped on Chicago Ave right in front of the Station, the two story building with the unusual roof line. It still stands today--I passed it this morning.