The Corn Palace in South Dakota is one of many reasons why the state's tourism is in full swing.

(Getty Images)

SPEARFISH, S.D. (AP) -- More than half a million people have visited the state's main tourist attractions so far this year as the state's tourism industry prepares for its busiest season of the year.

Ashley Worth with the South Dakota Department of Tourism says 518,000 people have visited South Dakota's National Parks -- Mount Rushmore, Wind Cave, Jewel Cave, Badlands and Minuteman Missile -- so far this year.

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She says that's a 25 percent increase through May.

Another 2 million people have visited South Dakota state parks through May.

Worth tells the Black Hills Pioneer (http://bit.ly/Mo7Mx9) that the mild winter and spring helped jumpstart South Dakota's tourism season.

Hotel operators throughout the Black Hills are also preparing for the season. Many operators report already seeing an increase in demand for lodging.