Gunnar Diepenbruck wondered several weeks ago whether or not an Apple LED Cinema Display could be connected in some fashion to the USB-C port of a 12-inch MacBook. I’d extend that question to ask about the Apple Thunderbolt Display as well. I waited to answer this to see whether a cable was forthcoming from Apple or third parties. None has yet appeared.
USB-C can carry DisplayPort data over the port, so this should be a possibility if the market were big enough to spur manufacturers. I have spotted one USB-C to Mini DisplayPort adapter for about $35, but it’s being sold under several names, and is manufactured by a generic-labeling firm in China. I haven’t yet tested it, and thus am not linking to it. The adapter is just for video, and thus no other USB devices (carrying power or data) can be connected to the MacBook if it’s in use.
Read more here:: How to connect an Apple Display to a USB-C MacBook