I'm loving Civ 5 so far, but I'm wondering if there's any way to boost late game performance.  By the time I hit 1700-1800, it can take a fair amount of time between turns.  I'm pretty sure this was an issue with Civ 4 as well, but I'm wondering if there's something I can do on my end to speed things up.  I don't think it's a problem with the specs on my pc, since it's pretty new and on the higher end. 

.....lol. 
 
Welcome to Civ V.

Larger cities. More stuff going on each turn because of the growth and the reveal of the map. It's just the game, but you could always play on easy so they don't build that much, or maybe choose a tiny map. 

They will keep optimizing it as time goes, but that will always be an issue with big maps.  Not sure if more memory even helps.

For the time between turns late game, I think cpu is the limiting factor. There's just too many calculations to be done.

This has been a part of grand strategy games since they were invented. As has been said in the early game there are fewer cities, units, and changes which have been made to the map so the turns zip by. However, as you get into the later game there are so many things happening each turn (units moving, engaging in combat, making changes to the terrain, building improvements to cities, etc.) that the computer has to go through each individual one deciding what it's going to do. So, it can take a hot minute and unless you're rocking a monster CPU you're going to have to wait a few seconds.
 
As an example of this I can remember playing Star Trek: Birth of the Federation about a decade ago. God I loved that game but when you got into the later years it became almost an unplayable mess. I don't know if it was my computer or the game but turns could literally take minutes. Maybe I'll try and dig it out of whatever box it's in in my garage and see if it'll run faster now...

To me it just seems like a matter of just how it is, not a performance issue. The game still runs the same but it has more to do. Each AI will have more units to move, cities to build in, population and tech tress to manage etc. I'm sure they can try and optimize it but it doesn't seem like there is that much they can do when as the game goes on the AI has more stuff to do.

See, the thing is that while Civ V isn't nearly as graphically demanding as a cutting edge shooter it is far far more computing intensive. Every turn the comp is having to decide what every unit, city, and everything else are going to do. By the late game that is taking a large large amount of effort.

Bumping this to get a sense of the latter game crashes that Civ V causes. It's pretty rediculous and such a glaring oversight. I meet the maximum requirements and yet I can only make a couple of decisions before the game just freezes up on me. Googling the problem comes with several other players experience game-freezing crashes like it. At first it occurred on the huge map / marathon game setting but now players are reporting it across many game mode types. I'm wondering if I'm not alone on this?

Haven't had this issue.
 
Lots of slowdown late game with loading and scrolling, but never any lockups even on huge maps with tons of civs and city-states.

I haven't had that issue. 

Civ V is heavily CPU-based. As you can see on these charts that used a late-game scenario benchmark, the game even scales with an overclocked Core i7 (when normally games would be based on the GPU, and would thus not scale with increased processor power). It's one of the few, if not only, games or game that is this dependent on the processor.  
  
(Charts from this article at Techspot)