Seventy years ago, as Allied troops stormed the fortified beaches of Normandy, thousands of workers in the Twin Cities cranked out ammunition used by those troops, and in the process, pumped much-needed vitality into the local economy.

Friday, on the anniversary of D-Day, officials from Ramsey County, the state and several local communities marked the end of demolition at the 427-acre Arden Hills ammunition site by swinging ceremonial sledgehammers in a redevelopment project they hope will transform a Superfund site into a new economic engine featuring retail, housing, manufacturing and recreation.

The county bought the Twin Cities Army Ammunition Plant site and began demolition and cleanup a year ago. Forty-three buildings have since fallen, their rubble carted away. Friday, work began to bring down the 44th and final building — Building 502.

"This is the last one," Ramsey County Commissioner Blake Huffman said.

Said Commissioner Rafael Ortega, who presided as board chairman when the county bought the site from the federal government last year: "This is the beginning of a great future for this place."

That future, according to a draft master plan of one of the largest undeveloped tracts of land in the metro area, is ambitious.

Plans call for 1,500 units of housing on 168 acres, 2 million square feet of office space on another 156 acres, 300,000 square feet of retail space on 18 acres, and 53 acres of open space that could include hiking and biking trails. Although officials say site cleanup won't be completed until October 2015, developers already are inquiring.

Arden Hills Mayor David Grant said it is only fitting that the site someday will infuse new economic life into the area. From 1942 through 1945, thousands of workers produced millions of rounds of ammunition for the soldiers hitting Omaha Beach and in other theaters of the war. The plant employed 26,000 people at its peak, helping lift the area out of the last doldrums of the Great Depression.

In a town — and county — that is otherwise fully developed, the 429 open acres of the plant site "is our future," Grant said. "Truly, at TCAAP, we are turning swords into plowshares."

Katie Clark Sieben, commissioner of the state Department of Energy and Economic Development, said the plant is not only a big deal to Arden Hills and Ramsey County, but it is one of the biggest redevelopment projects in the state.

"It hasn't been a job provider for decades," she said. "And it's time we changed that."

Barbara Gertsema of Minneapolis and George Johnson of Ham Lake were among the last to work at the plant, before it was abandoned and Federal Cartridge and Alliant Techsystems still had operations there. Gertsema was an administrative assistant for environmental cleanup for 18 years. Johnson worked on electrical and mechanical systems into the early 1990s. Both spent time working in Building 502.

"What's here today, now, this is sad," Gertsema said of the plant's dormant years before redevelopment work began last year. "But this, this is progress."

James Walsh • 651-925-5041