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KANSAS CITY, Kan. — The Missouri River 340 Race attracts paddlers from around the globe. Over the next three and a half days they’ll travel 340 miles from Kaw Point in Kansas City, Kan., to St. Charles, Mo.

Organizers say it’s the world’s longest non-stop canoe and kayak race.

The Missouri River 340 Race has been named one of National Geographic’s top 100 American adventures. Competitors get 88 hours to complete the course. Along the way they have to sign in and out at checkpoints along the river.

Organizers say it’s an extreme sport that benefits a good cause. All proceeds go to help preserve, maintain and beautify the Missouri River.

Organizers also say the race celebrates the importance of the Missouri River as a source of drinking water for millions.

The first set of paddlers headed out at 7 a.m. on Tuesday. They are expected to make it to Jefferson City by Wednesday morning and to St. Charles by Wednesday night and early Thursday morning.