The easiest and most cost effective way of traveling in Chicago when walking isn’t practical is taking the “L” trains. They’re called the “L” because they’re elevated… except a few of the stops are actually underground. (Adding to the confusion, the regional Metra rail network also runs on elevated tracks in certain places.)
Each “L” train has a color and a destination. Your best bet for finding your way around is Google Maps — not only does it tell you where to get on and off, it provides up to the minute notifications of delays.
The “L” is run by CTA, which also runs the local buses in Chicago. Personally I never used their buses but depending where you’re going it may make more sense.
Both the “L” and the CTA buses take the reusable Ventra card which you can buy for $5 at any CTA ticket vending machine. If you register the card online you get your money back in $5 worth of transit credit on the card.
You can either pay per trip or buy one of several day/multi-day pass options with unlimited rides. These passes are surprisingly inexpensive, particularly if you compare the cost to Uber or a taxi.
If you’re not interested in buying day passes I’m told you can also pay with your phone if you have a phone that supports Apple or Android Pay. In practice I didn’t try this or see anyone else pay this way either.
Tourists should note that the “L” goes to both Midway and O’Hare airports. It doesn’t go directly to Amtrak’s Union Station but there is an “L” stop a short walk away.
Do be aware that the above ground “L” lines can be very loud — not so much inside the train but outside. You’ll definitely hear when they’re going over, particularly on drawbridges or around corners. This is something to consider when you’re looking for a place to stay or at the very least whether or not to bring earplugs.
The “L” is such a defining feature of downtown Chicago that the neighborhood is called “The Loop” because of the circular above ground track loop. Additionally, both the red and blue lines go underground within The Loop.
One unusual feature of above ground rail in a city filled with high rise buildings is you can often see right inside the buildings. I’m sure nobody would appreciate it if you brought binoculars to spy on office workers while waiting for your train.