STURGIS, S.D. (AP) -- Politicians joined bikers Monday in unveiling four commemorative postage stamps dedicated to the American motorcycle at the biggest gathering of bikes, the Sturgis Motorcycle Rally.

About 350 motorcyclists then set off for a 100-mile tour of the Black Hills in the annual mayor's ride.

"When you ride a motorcycle, you experience life through all of your senses," said James Miller III, chairman of the U.S. Postal Service Board of Governors. "Four wheels move the body but two wheels move the soul."

The stamps replicate a 1918 Cleveland, 1940 Indian, 1965 Harley-Davidson Electra Glide, all of which were on display, and a 1970s chopper that was created by an artist and will be built.

A hundred years ago, the post office used motorcycles to help carry the mail, so the agency has a historic connection to the bike, Miller said.

Besides Mayor Mark Zeigler, political leaders attending the dedication included Gov. Mike Rounds, Utah Gov. Jon Huntsman, U.S. Interior Secretary Dirk Kempthorne and South Dakota's congressional delegation: Sens. Tim Johnson and John Thune and Rep. Stephanie Herseth.

Rounds, Huntsman and Kempthorne also took part in the mayor's ride.

Kempthorne, whose father grew up in South Dakota, owns a Harley-Davidson but rode a Harley belonging to Steve Oberg of Rapid City, a member of the National Guard who injured his leg in Iraq.

"He's allowing me to ride his motorcycle today so I'm going to ride for Steve," Kempthorne said.

After the stamp dedication, those gathered under a large tent went out to the rows of motorcycles, started their engines, lined up and took off for a ride through the Black Hills to Crazy Horse Memorial, then a barbecue at the state game lodge in Custer State Park.

The riders paid $50 to take part. Proceeds go to the Sturgis Fire Department.

Jason and Cherie Blevins of Bellavista, Ark., had heard about the ride before but it was their first.

"Just wanted to do something different this year than the normal rides," she said.