Hmm... 16 responses and not a single person asked "Why?"

Is it because I'm on the East Coast?

Why would such a system be abandoned? It's not like someone laid tracks across a farm!
I can not imagine a such a vast system of underground tunnels that were once heavily used suddenly become of no value - did everyone in LA buy a car on the same day?

Or are these pics of poorly planned expansions which never occurred? Or as someone mentioned above - maybe the system was condemned for safety reasons. Verse repaired?

Interesting pics - reminds me a bit of a line in NY that runs to an opulent station which is rarely open to the public, though passengers can now see it from a train passing through:

NYC City Hall abandoned station

At one time in Philly, there was a proposed and partially built subway station near US-1 for a subway line never built for travel into Northeast Philadelphia. It was lost forever after the SEARS building was imploded. I think SEARS spent a million dollars anticipating future traffic in and around it's building /store.

Philly subway to the Northeast

/Mitch