One of the features Apple touted as An Official Awesome New Thing™ about Mavericks is that you can have your Dock and your menu bar appear on a secondary display. That’s pretty cool, I think, but if you’ve gotten accustomed to the old behavior, you can revert back to it if you want to. The setting’s in a place you might not expect, though—it’s within System Preferences> Mission Control, and it’s labeled “Displays have separate Spaces.”
Turn that off, and Mission Control preferences will warn you that you’ve gotta log out for the changes to take effect.
After you do that, the behavior will switch back to what happened under Mountain Lion. You won’t see a menu bar on your secondary display, nor will you be able to invoke the Dock by dragging your cursor to the bottom of the screen. I like the new Mavericks changes, but it’s nice to know how to switch things back if we need to, isn’t it?