PEMBINA (AP) - Orlin Ostby has guided an ox cart along the 420-mile Pembina Trail from Pembina, to St. Paul thousands of times - in his mind.

On Monday, he started the journey for real, to observe Minnesota's 150th anniversary as a state and 50 years after he helped a neighbor and friend, Delmar Hagen, prepare for a similar trip for Minnesota's centennial.

"It's just something I have to do," he said Monday, as he secured the near-replica of a 19th-century ox cart to Pum, a 5-year-old, 2,600-pound ox steer.

Traveling an average of eight miles a day, Ostby plans to reach St. Paul during the Minnesota State Fair set for Aug. 21 to Sept. 1.

His trip is a re-enactment, a journey honoring the fur-trading era in the history of Minnesota and North Dakota. Between 1849 and 1901, as many as 500 ox carts traveled in procession between Winnipeg and St. Paul, carrying furs to St. Paul and returning with goods used by the early settlers. The ox carts were driven by the Metis, a culture that descended from French voyageurs and Ojibwe.

Ostby, who lives on a farm near Gatzke, Minn., was a teenager when he helped train a shorthorn oxen steer named Napoleon for Hagen. After several years, Ostby dropped off Hagen, Napoleon and his two-wheeled wooden ox cart at St. Vincent, Minn., just across the border from Pembina.

"You could do this for Minnesota's 150th birthday in 2008," Hagen told the 17-year-old Ostby at the time.

"I never forgot that," Ostby said. Finally, in the fall of 2002, he and his family started planning the ultimate adventure.

They found a boy in New Hampshire who was raising oxen as a 4-H project. Thomas Philbrick and his family ran a pumpkin farm. So, they named the two young Holstein steers Pum and Kin. The Philbrick family delivered the two oxen to the Ostbys in the summer of 2003.

"As long as I've known Orlin, he's talked about doing this," his wife, Mandy, said.

It has become a family adventure for the Ostbys, who also raise livestock, dairy cows and draft horses, in addition to farming small grains. Orlin also works at Polaris Industries in Roseau, Minn.

They've been walking Pum about 8 to 10 miles a day in preparation for the trip.

Mandy, 17-year-old son, Christopher, and 12-year-old daughter, Cathryn, are making the journey, walking along Orlin and following in support vehicles. They're also accompanied by Steve Reynolds and Jackie Helms of Wannaska, Minn., and other friends and family.

They'll stop for special events along the way. Two of them include Marshall County Park in Florian, near Stephen, Minn., on July 5, and Old Mill State Park on July 6.

Thomas Philbrick and his father, Jeff, will join the caravan when it gets closer to St. Paul.

The family is inviting people to walk with them, for just a few hours or a few days. They have a Web site, www.walkingthepembinatrail.com, and will keep a journal.

The route they are traveling is the Woods Trail, one of three Pembina Trail routes.

The family is raising money through contributions from the public and from local historical societies along the trail.

The event also is partially sponsored by Palmville Press and Publishing Inc. of Wannaska., Minn., operated by Steve Reynolds.

"We've been working at this for a long time now," Ostby said, as he walked with Pum over the Red River east of Pembina on Monday. "It's going to be hot. But we expect he'll be OK. If it gets too warm for him, we're going to haul him for a while."

As for Ostby and his crew, he said, "Delmar was 15 years younger than me when he made this trip," he said. "I figure Steve and I will probably drop about 45 pounds on the trip. Pum, too. But we all can probably use it."