The "most historical pieces" that failed and led to the Interstate 35W bridge collapsing in a deadly heap into the Mississippi River six years ago were turned over Thursday to the Minnesota Historical Society for eventual public viewing.

The Minnesota Department of Transportation transferred to a Historical Society storage facility in St. Paul four pieces, two of those the gusset plates that investigators determined gave way under the road surface, leading to the downtown Minneapolis bridge's failure.

The plates, along with two large beams that round out the four pieces, "we felt were the most historical pieces [and] probably in many ways the missing pieces to telling this story," said Adam Scher, the Historical Society's senior curator. "They really tell the story in the most tangible way of the collapse itself, especially since we have the gusset plates."

The plates and the two beams come from "basically the same part of the bridge," Scher said, specifically the area that federal investigators identified as the most likely point of failure for the bridge during afternoon rush hour on Aug. 1, 2007. Thirteen people were killed in the collapse and another 145 injured.

One steel beam weighs 6,800 pounds, this being the one that had the two gusset plates attached. The other beam is about 2,400 pounds. One of the plates had a small piece cut off during the federal investigation, and that slice went to the Historical Society.

Scher said the Historical Society has yet to discuss when the pieces will go on exhibit at the Minnesota History Center in St. Paul, but he's sure that day will come.

"It's a compelling story," he said, "an important chapter in Minnesota's history. That's the reason that we are preserving them."

Other items the Historical Society has in connection with the collapse include a Red Cross first-responder's shirt and road signs from the bridge.

Following approval from the Legislature, the state was cleared to turn over pieces of the bridge to survivors, loved ones who lost relatives, universities and civic groups as well as the Historical Society.