McMillan Grange Mutual Fire Insurance Company was organized on the 28th day of May, 1898. A board of nine members was elected and from the nine a President, Vice President, and Secretary-Treasurer were chosen. The Company started writing fire insurance policies on August 15, 1898.
In the early years, the company made an assessment to their policyholders to assist in the paying of losses. However, on April 12, 1933, a reinsurance program was voted in place, which eliminated the assessment program.
A special policyholders meeting was held July 19, 1957, at which time it was voted to insure against windstorm and hail losses. On August 10, 1962, the board approved to write farm blanket coverage. Over the past several years, many additional special coverages have been added.
At the annual meeting held on February 11, 1969, it was adopted to change the company name to McMillan Mutual Insurance Company.
A new office building was constructed in 1969, and an open house was held November 7, 1969. This is the building that is currently used today.
On April 30, 1982, the company merged with the Warner Mutual Insurance Company; and therefore the name was changed to the present name McMillan Warner Mutual Insurance Company.
On January 1, 2000, McMillan Warner Mutual Insurance Company converted from a Town Mutual Insurance Company to a Domestic Mutual Insurance Company.
On January 1, 2005, the company merged with Lindina Town Mutual Insurance Company in Mauston, Wisconsin. With this merger, the company formed The Lindina Insurance Agency, a wholly owned subsidiary of McMillan Warner.
On October 1, 2017, McMillan Warner merged with Calumet Equity Mutual Insurance Company of New Holstein, Wisconsin. The office location in New Holstein will remain open as a branch office of McMillan Warner Mutual Insurance Company.
McMillan Warner Mutual Insurance Company is a policyholder owned domestic non-assessable mutual insurance company.