The Census Bureau has put out an interactive mapping tool for finding out Census Mail Participation Rates for 2000 & 2010. This tool goes down to the census tract level, and will also give you a snapshot of an area using colors representing participation rates. Data is updated Monday through Friday, and is so pretty close to real time.
Right now Minnesota is at 29% with the National rate being 20%. In 2000 MN returned 78% while nationally the rate was 70%.
It's really important that MN has a high response rate for the Census; millions of dollars and a seat in the House of Representatives are at stake.
Government Documents Coordinator.