Actually Connie, there are a number of cannon manufacturers around.

The best (in my opinion) are;
http://www.specialtymile.com/southbendreplicas/
http://www.pbocorp.biz/
http://www.steencannons.com/
http://www.cannonltd.com/

A couple other great websites that will give you plenty of information on CW artillery are;
http://www.civilwarartillery.com/
http://www.cwartillery.org/artillery.html

Michigan really isn't that far away.