The pilot, who was not identified, was being treated for serious burns and injuries, according to the Washington County Sheriff's Office. No one else was on board the blimp.
The incident occurred near Erin, Wisconsin, about 45 miles northwest of Milwaukee. The sheriff's office said the blimp may have experienced mechanical problems prior to the crash.
The blimp crashed in an open field about a half mile (one km) from the Erin Hills golf course around 11:15 a.m CDT (1615 GMT), according to a statement from the U.S. Golf Association.
Some witnesses reported on social media that the blimp was on fire and smoking before it hit the ground, and smoke was visible rising among the trees after the crash.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
"I was teeing off and I looked up and saw it on fire, and I felt sick to my stomach. I had the shakes. I felt terrible for the people inside," golfer Jamie Lovemark said at a news conference.
Golfer Brandt Snedeker said his caddie pointed it out on the 9th hole. "He said the blimp is not looking good," he said to reporters.
The blimp, not affiliated with the U.S. Open, was operated by Airsign, a Florida-based company, to display advertising, Airsign sales manager Catherine Walsh said.
The National Transportation Safety Board said it would investigate the incident. According to the sheriff's office, the blimp had been airborne for several hours prior to the incident and was lawfully operating at the proper altitude.
"Our thoughts and prayers are with the pilot at this time," the USGA statement said.
(Reporting by Larry Fine, Chris Kenning, Frank Pingue and Steve Keating.; Editing by Dan Grebler and Cynthia Osterman)
