PIERRE, S.D. (KELO) -- Hundreds of people turned out Monday morning to witness something that for many was a once in a lifetime experience. Construction experts demolished the old bridge that had stood since the 1960s across the Missouri River between Pierre and Fort Pierre. Mountain lion rescued from tree in Rapid City The giant span was replaced last year by a new bridge between the two cities. Missouri River bridge between Pierre and Ft Pierre as steel girders hit the water.Missouri River bridge between Pierre and Ft Pierre as steel girders hit the water.Missouri River bridge between Pierre and Ft Pierre as steel girders hit the water. Crews this winter had already removed the concrete bridge deck on the old bridge. Traffic on US 14 and US 83 was diverted from the new bridge for a half hour on Monday starting at 9 a.m. The blast took down the steel framework of the old bridge. People watched the girders drop neatly into the water, then saw black smoke from the explosives. Milliseconds later they felt the shock from the blast. Still standing undamaged upstream were the new bridge as well as the old railroad bridge that carries train traffic on a regular basis. John Simpson of Pierre was among the people who turned out to watch the historic event. "I saw the old bridge go poof," Simpson said. "It was an amazing event. It happened so quick, and so precise," he continued. "There were just two or three more dozen charges that all went in a puff of black smoke in an instant. And that bridge fell slowly and gradually -- just like you think it would happened a little bit quicker, but all of a sudden it was in the water and it's gone. And a whole bunch of black smoke came floating over the scene, very low wind so the smoke kind of hung there, obscured the view for a little bit -- really an amazing sight to see." Police watercraft and other security kept boaters a safe distance from both sides of the bridges. Boat traffic and pedestrians will be kept out of the immediate area for the next 24 hours. Crews using cranes on barges will now remove the steel girders from the water, according to the South Dakota Department of Transportation engineer for the Pierre area "The contractor will utilize strategically placed barges, buoys  and lights to keep river enthusiasts out of areas where cleanup is commencing and direct boaters where they can safely pass through," Dean VanDeWiele told KELOLAND News. ...read more read less