The exact moment in time that Rochester officially became a city of the first class. Here is a note from City Attorney, and Fighting Sioux Alum, Terry Adkins.
I just received a phone call from the Secretary of State’s Office. A certified copy of the 2010 federal census was filed in their office at 9:00 am on March 17th . Pursuant to the provisions of Minn. Stat. §410.01, the City of Rochester is now officially a City of the First Class.