There is no “made in” mark on finished drywall, so you can’t tell the origin by looking at it. And most of the time the drywall installer orders from a supplier who delivers it to the jobsite, so the guy who hung the drywall probably wouldn’t know either. If your house was built between 2002 and 2007 and smells like rotten eggs, you might want to investigate further.
That and gypsum mined here can probably be differentiated from that mined in China.
Unfinished drywall is marked. If your drywall is covered over with mud and paint, you might try obtaining a copy of the contractor’s invoice for the wallboard. The problem with composition in at least some products might be overages of cellulose rather than sulfur. As for American producers, check documents from lawsuits against National Gypsum (Charlotte, North Carolina) and Atlanta-based Georgia-Pacific Corp (Atlanta, Georgia).
U.S.-made drywall also being investigated
http://www.msnbc.msn.com/id/34154003/ns/business-us_business/
I avoid wallboard and most other products from China and our east coast.