Oops: Bernie Sanders refers to Sioux Falls by wrong name

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U.S. presidential hopeful Bernie Sanders began his campaign rally in the South Dakota city of Sioux Falls with a geography blunder.

The Democratic senator from Vermont referred to Sioux Falls as Sioux City, which is in Iowa.

That prompted groans and boos from the crowd. Sanders quickly realized his mistake and corrected himself.

President Barack Obama made the same mistake when he campaigned in Sioux Falls in 2008.

Sanders is competing with Hillary Clinton for the Democratic endorsement. Whoever gets it likely will run against presumptive Republican nominee Donald Trump. Sanders held campaign rallies in Pine Ridge, Rapid City and Sioux Falls on Thursday.