Whether they are worth anything in the monetary sense depends entirely on their condition, what a buyer would be willing to pay, etc. Their real worth lies in their historical significance and the considerable role they play in the overall architectural integrity of the building they are in.

IMHO, the fad for removing beautiful old windows, tossing them in the landfill and replacing them with short lived "energy efficient" replacement windows is an ongoing tragedy and a huge consumer fraud.

Unless they are hopelessly damaged, old windows are superior to any you could buy today and are well worth repairing. Read the fine print in today's replacement window advertising and see if you think any are likely to be around as long as ones made in 1834. Old windows fixed, weather stripped, supplemented with high quality exterior and perhaps interior storm windows, will be just as "energy efficient" as the over-hyped stuff you can buy with their phony claims and short life spans.

I see them advertised some on craigslist. Not worth big money, usually around 10 or 20 a window for crafters to buy and use on projects. I have one myself that I painted a design on and it hangs in my house.
Cher

These windows, if original, were probably fabricated on site and cannot be easily removed and reinstalled elsewhere. Often all that can be saved are the sash. I would say the only thing that would be valuable is the glass if it is original.

Ditto everything mainegrower said. Please please please don't rip out your windows.