MINOT (AP) - Rick and Mary Ellen Thibodeau figured the Rocky Mountains would be their biggest challenge in a bicycle ride across the northern United States. They found North Dakota offered a challenge of its own.

It was on a stretch of state Highway 1804 from Williston to Lund's Landing on Lake Sakakawea.

"I've been riding for a long time, and it was probably the most difficult 20-mile stretch I've ever ridden," said Rick Thibodeau from beneath the covered porch at Lund's Landing Resort. "I didn't have to get off my bike, but it was tough."

Mary Ellen, his wife, said she also considered the curving uphill-down stretch of the North Dakota highway more challenging and demanding than the snowcapped peaks rising above western Montana.

"It is the hardest stretch we've gone so far, including going over the Rockies at Lolo Pass," said she said, laughing. "We were hot and tired."

The couple, from West Harford, Conn., said they began their cross-country journey on June 4 at Astoria, Ore., hoping to cover the 4,000 miles that will take them to Westerly, R.I.

They chose a northern route because of the Lewis and Clark Trail and the chance to meet everyday people.

"We wanted to see the country in a very different way and to meet people, ordinary people," Mary Ellen said. "We're not going to what you would consider big tourist areas. We're taking back roads and going to small towns. It's really very easy to strike up conversations with people."

It was a 35-year wedding anniversary trip, Mary Ellen said. The couple also wanted to raise money for the American Cancer Society and celebrate her fifth year of being cancer-free, she said.

The couple have a Minot connection of sorts. Mary Ellen works for ING in Hartford, which also has a branch in Minot.

Rick Thibodeau removes a laptop computer from his saddlebags each night and logs the distance traveled, the name of the place where they spend the night and makes notes about the events of the day. The only problem the couple reported was a couple of flat tires.

After leaving North Dakota, the Thibodeaus' route will take them through Minnesota, past the Erie Canal and then on to Buffalo, N.Y. They hope to reach Rhode Island by Aug. 15.