The plants employ about 4,300 hourly and salaried workers.
"A decision to end production at a plant is not an easy one, and I'm deeply mindful of the impact this decision has on Ford employees, families and communities," Mark Fields, Ford's president of the Americas, said in a statement. "Unfortunately, these are necessary steps we must take to move the business forward."
Local UAW 879 president Rob McKenzie in Minnesota refused to comment, but said the union would hold a news conference Thursday afternoon.
The closing of the Norfolk plant, which employs about 2,400 workers and makes F-150 pickup truck, will also impact 400 employees who work at affiliated auto parts facilities close to Norfolk, Kimmons said. The Ford plant is expected to close by 2008, he said.
"It's all about the dollar signs," Kimmons said. "Even though we're the best quality plant in the Ford system, it comes down to the dollar."
The Twin Cities assembly plant makes the Ranger pickup, which has seen sales decline sharply in recent years. It employs about 1,775 UAW members.
In January, Ford named five plants it planned to close and said it would name two more plants later in the year.
Plants already announced to be idled by 2008 include the St. Louis, Atlanta and Wixom assembly plants and Batavia Transmission in Ohio. Windsor Casting in Ontario also will be closed, as was previously announced following contract negotiations with the Canadian Auto Workers.
"These cuts are a painful last resort, and I'm deeply mindful of their impact," said Ford Chairman and Chief Executive Bill Ford in January, unveiling the "Way Forward" plan to boost profits. "In the long run we will create far more stable and secure jobs. We all have to change and we all have to sacrifice, but I believe this is the path to winning."