CHICAGO, July 5 (Reuters) - The Mississippi River, the most important U.S. commercial waterway, reopened to water navigation on Saturday after much of it was closed for nearly a month due to the worst flooding in 15 years.

"As far as navigation, the river is open," said Steve Farkas, an engineer in the U.S. Army Corps of Engineers' St. Louis office.

Lock 25 near Winfield, Missouri, north of St. Louis, was the final lock to reopen and it reopened Saturday morning, Farkas said.

Taller river traffic will continue to be impeded until a railroad drawbridge, which spans the river about 60 miles (97 km) upriver of St. Louis, is repaired later on Saturday, the Kansas City Southern <KSU.N> railroad said.

Water levels have been dropping, but remain above flood stage. Near St. Louis, the Mississippi River was 7.1 feet (2.2 meters) above flood stage Saturday morning, which was down from Monday when it crested at 8.3 feet (2.5 meters) above flood level.

"Everything is going down," Farkas said of the water.

At the height of the flooding, which began in early June, nearly 300 miles (480 km) of the Mississippi River was closed to barge traffic, disrupting shipments of grain, coal, and petroleum products.

The river is the main channel for grain flowing from fertile Midwest farms to export terminals at the Gulf of Mexico.

The flooding has caused billions of dollars in damages and wiped out millions of acres (hectares) of corn and soybeans and sent grain prices to new highs this summer.

(Reporting by Bob Burgdorfer; Editing by Eric Beech)

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