Greetings...
Quick question about building railroads in captured lands. For a while after I take over cities/land in another continent, I cannot get my workers to build railroads. Then it will allow it. Is there a prerequisite for this, say a harbor to your homeland or something ??

-Stealth

You likely need access to coal (maybe iron) in the new continent. Check one of your cities there to see what resources they have. If they are missing them, build a harbour (to trade with your home continent) or find local sources.