I’m not a well traveled guy but I just always assumed that a city would only get either a subway or an elevated rail system. Do any of the big cities have both?
Yes, I could google but I don’t wanna read through a dozen wikipedia articles about the history of public transportation in a dozen countries:p
Chicago has both subways (the Red and Blue Lines in the Loop and a handful of other locations) as well as elevated trains (the iconic L, for the majority of its length). They are part of the same system (so the Red Line and Blue Line are at times underground, other times elevated, and sometimes even at grade).
New York City has both a subway system and elevated rail. The els were there first, with subway added later.
LA has a bit of both (and not enough of either). Gold, Blue, and Expo lines are above ground for the most part. (I think. Actually, I’ve only ever been on the Expo line). Red and Purple lines are entirely below ground.)
ETA: Oops, reread and you’re looking for elevated, which knocks out Blue and Expo I think. But the Gold line has at some parts at least somewhat elevated.
London, I’m going to have to call a PITA for not using even Google.
PITA
Peter
Chicago and New York have both, but they’re not separate systems. A single line can be elevated, underground, or on the surface in different places.
You could’ve just picked one or two.
NYC
Chicago
London
It’s been a really long time, but if memory serves I think the lines in Philly are partially below ground, partially elevated.
I would guess that most cities with a rail system have sections that are underground in high density parts of town and surface and elevated sections in outer parts of the network. The Washington DC Metro includes sections that run as subways, surface lines, and elevated lines.
Panama City is currently building a subway system that will include both underground and elevated sections.
Bangkok has the Metro and the Skytrain, and they’re separate systems. In addition to that, the Airport Rail Link is a separate system of its own.
German cities often have separate S-bahn and U-bahn systems, and both can have elevated and underground sections. The first is more of a suburban rail type system with fewer stops, while the latter is your classic metro type system. They’re more or less integrated with each other depending on where you are. Paris has something similar with the Metro and the RER.
In a lot of places there’s also often a light rail or tram system on top of that.
Anyway, there’s bound to be loads of examples of this kind of thing, and usually more complex than simply subway vs. elevated. Different rail-based transit systems in one city, more or less integrated with each other in terms of station transfers and ticket systems, and using different combinations of underground, surface level and elevated sections, is probably more the rule than the exception.
Vienna and Copenhagen are other cities that come to mind with a combination of metro and S-bahn (called S-tog, “S-train”, in Copenhagen).
The SF Bay Area has the BART system, which is at times elevated, street level, underground, and underwater.
Atlanta’s MARTA system runs underground, elevated and ground level.
ETA Part of downtown is elevated and MARTA runs at ground level under it.
Yes.
Huh, when I was living in the Philadelphia area, I never noticed any elevated lines. The trains I saw were all underground downtown, and at ground level in the outlying areas.
St. Louis runs its light rail through the old railroad tunnels downtown, then a mixture of surface and elevated farther out.
Boston’s subway system has underground and surface-level parts, and a little bit of elevated track.
Basically, this thread will now proceed to list more or less every large city in the world. 
The thing is, “either a subway or elevated rail, or both” just isn’t a very useful or descriptive way of thinking about rail-based public transit, anywhere.
It might be more useful to list the exceptions that consist of only subway, or only elevated lines - which mostly would be pretty small systems, I think.
Buffalo is one such example. The rail is ground level downtown and underground as it goes out of the city. There are no elevated tracks. Of course, it’s also just one line.
I know what you mean, but it brings to mind the question, “Did you remember to bring your SCUBA gear, Dear?”