EXHIBIT 16.1 Wipfli Ullrich Bertelson LLP 469 Security Blvd. Green Bay, WI 54313 PO Box 12237 Green Bay, WI 54307-2237 (920) 662-0016 Fax: (920) 662-0024 www.wipfli.com August 29, 2002 Office of the Chief Accountant Securities and Exchange Commission Mail Stop 9-5 450 Fifth Street, N.W. Washington, DC 20549 Dear Sir or Madam: We have read the statements made by Blackhawk Bancorp, Inc. in Item 4 of Form 8- K dated August 28, 2002, which we understand will be filed with the Commission. We agree with the statements concerning our firm in such Item 4 of Form 8-K. We have no basis to agree or disagree with other statements of the Company contained therein. Sincerely, Wipfli Ullrich Bertelson LLP