Why are commodoties dollar-denominated? How was the arrangement reached?

Question

What other things are solely dollar-denominated?

Answer 1

Perhaps because the world's biggest commodity markets are in the U.S.?

http://en.wikipedia.org/wiki/New_York_Me...

http://en.wikipedia.org/wiki/Chicago_Boa...

It could also be because the U.S. has been the single largest purchaser of commodities until very recently (China now purchases more of some commodities)

But the answer you are probably looking for is the formal one. As part of the Bretton Woods agreement, the dollar was made the world's formal reserve currency:

http://en.wikipedia.org/wiki/Reserve_cur...

and even though this agreement didn't last for very long, the dollar is still the primary reserve currency in the world.