For months now Chicago has been a major location for the "Transformers 3" crew where several key scenes have been filmed. In the final days of filming, Mayor Daley held a press conference with "Transformers 3" producer Lorenzo di Bonaventura. Economically speaking, the filming had a huge effect. According to the article:

"...benefits to Chicago that go far beyond the 1,200 jobs and $20 million pumped into the local economy."

You can read the entire article on the Sun Times web site.