Ninety-nine years to the day after it opened, the walls of the former General Motors assembly plant in Janesville started coming down. Missouri-based Commercial Development Company is re-purposing the huge property. It is expected to take 12-to-18 months to demolish the four-point-eight-million square foot building where thousands of people worked over the decades. The assembly plant opened its doors May 1st, 1919, and was shut down nearly 10 years ago. C-D-C bought the property in December with plans to redevelop it. Owners say they have already received “significant interest” from prospective occupants.