With the new expansion coming out next month, I was wondering if anyone has any ideas on what happened to Pittsburgh in the Fallout universe.

I keep seeing references to it being an "industrial" city, but Pittsburgh hasn't been considered industrial since the late 70's. It's now better known for medicine and technology. Sadly, the rivers ARE horribly polluted, but the days of smoke-filled skies were over 40 years ago.

Fallout is set in an alternate timeline that diverged from ours in the 1950s. In the 21st century, it looked like the future as imagined in the 1950s pulp science fiction. E.g. instead of transistors you have huge vacuum tube-based computers with artificial intelligence and monochromatic terminals, robotic servants, a pseudo-utopian society based on 1950s values, black and white TV, music from the 1950s considered all-time classics, and most modern musical genres never appearing, etc,. Weapon development was also different from ours and thus plasma and laser weaponry was introduced, 10mm became the most common ammo type, etc. The modern high-tech weapons were never created - instead, weapons based on how people in the 1950s thought 21st century weaponry would look like are used.

And looks like Pittsburgh never stopped being an industrial city.

For more information, see:

http://fallout.wikia.com/wiki/Fallout_world
http://fallout.wikia.com/wiki/Divergence
http://fallout.wikia.com/wiki/Timeline
http://fallout.wikia.com/wiki/The_Pitt

The Pitt didn't get nuked, so there were a lot more people. Since the rest of the world was busy getting wiped off the map, I'm guessing people went nuts there.

And then the tin can brigade scourged the place.

It wasn't hit directly by nukes, but was still affected by the fallout.

That, and the rivers.

Well not being directly hitted by the nukes, the three radiated rivers caused a lot of problems on there own, people started mutating and such ... , 30 years ago or so the more holy than holy knights named the BoS under Lyons and Casdin did a bit of mutant extermination in that area and did take children who were not mutated with them to be trained as more holy than holy knights.

Somewhere there Casdin and Lyons didn't exactly agree, and Casdin left Lyons and his group not exactly on friendly therms