From the FAQ section of the National Register of Historic Places

-http://www.Nps. Gov/history/nr/faq.htm

How do I apply for grant money or tax credits?

The National Register of Historic Places does not have a grant program ourselves. However, Heritage Preservation Services (a different division of the National Park Service, Cultural Resources Program) does have a tax credit program that may be of benefit to you.

The website for the tax credit program is:
-http://www.Nps. Gov/history/hps/tps/tax/index.htm

Additionally, sometimes state historic preservation offices may have state run programs that could help.

You can find contact information for the SHPOs at
-http://www.Nps. Gov/history/nr/shpolist.htm

Here’s the link for the Wisconsin Historical Preservation Society

-http://www.Wisconsinhistory.org/hp/

Learn how the Society can work with you to identify and protect archaeological sites, burial places and historic buildings in Wisconsin.

As the federally designated State Historic Preservation Office, we supply a variety of preservation tools for you whether you are a property owner, a government official, or an interested citizen.

I don’t know how much this will help you, but here’s an article I found on the subject of grants and how to obtain them.