Just a few years ago, David Darby used a lot of energy trying to explain why historic U.S. 6 is so special. It's the first paved road to stretch all the way across the United States, including Iowa.

"It used to be an uphill battle to explain Highway 6," said Darby, of Davenport, the executive director of the Iowa U.S. Route 6 Tourist Association that is based in Davenport.

His concept is better understood today. This year's River-to-River Classic Car Retro Road Trip has at least 100 participants — probably more like 150 or even 200 cars. Drivers will cross a beautiful slice of Iowa, off the interstate highways and along the two-lane road.

The event kicks off in downtown Davenport at 10 a.m. Friday, Aug. 23, and follows the historic road west across the state until the cars cross the Missouri River into Omaha, Neb. Participants can pose for an All the Way Club photo in Council Bluffs, Iowa.

"I think it's neat that Darby found the old route through all these towns in Iowa," said K.V. Dahl, the president of Dahl Ford in Davenport and a participant on the upcoming drive. Dahl will ride with three family members and drive four classic cars, including 1957 and 1966 Ford Thunderbirds.

"I love to exercise these cars on those two-lane roads and follow the whole route through Iowa," he added.

Drivers are invited to start with the parade in Davenport or join at any point on the route across the state.

Darby has a lifelong interest in cars and said he remembers well using U.S. 6 when his family camped on the Cedar River near Moscow, Iowa.

"Those towns on that road used to thrive," he said, with motels, gas stations and restaurants that are slowly disappearing.

Some 16 Iowa towns were bypassed when Interstate 80 was built, Darby said, and officials routed the four-lane interstate along parts of the former highway, especially in Scott County.

Darby hopes to help the Highway 6 communities rediscover their roots as well as to help drivers remember why it is a good choice to cross the state on the road.

Found it in Connecticut

Darby was in Danbury, Conn., a few years ago when he noticed Highway 6 signs on the streets, linking the road to its location in Davenport. Some Connecticut friends wanted to tour Iowa, and Darby recalled how he used to admire historic Route 66.

He suggested the Connecticut visitors use U.S. 6. That was in 2008, and he recruited a couple of friends with classic cars to go along.

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Flash forward to 2011: Darby started a book on the roadway ("From River to River: Your Guide to the Original Highway 6"), a campaign to purchase historic signs and directed the first drive.

The 2012 version was a success, and Darby is overseeing a much bigger event this year. Right now, he is busy getting the brown "Historic Route 6" signs up along the way and has erected more than 60 of them. A goal this year is to install them completely though Iowa City, with the entire sign project to be finished in 2014.

This requires the cooperation of state and local officials, but Darby is finding it a much easier sales pitch than it once was. Many tourism experts, for example, quickly see the value of the celebrated roadway, which also serves as a memorial to the Grand Army of the Republic, a fraternal organization for Civil War veterans.

The road was planned in the first part of the 20th century, and by 1937 it stretched from Provincetown on Cape Cod, Mass., to Long Beach, Calif. It used to run from Illinois over the Government Bridge into Davenport and up Perry Street, Darby said.

Stretches statewide

This year's event will continue west out of Davenport to Walcott, Durant and Wilton, Iowa. Stops include the Hill of Beans Bistro in Durant and the historic Wilton Candy Kitchen.

Farther west, the town of Brooklyn, Iowa, will close off streets for a parade, while costume contests and other events are planned in Grinnell, Newton, Des Moines and Atlantic.

"This is just a really neat event to showcase the real Iowa," Darby said.