The American Bank first opened its doors in 1896 under the name of The Farmers Bank and was located in the 200 block of South Main Street in Cuba City. It was started by John Longbotham, George Loeffelholz and John Warwick and was at first a private, uncharted bank.

In 1903, application was made and granted for the bank to become a Wisconsin State chartered bank. In 1910, the name was changed to the Cuba City State Bank. In 1928, the bank acquired ownership of the First National Bank, its only competitor in Cuba City, and subsequently moved into its building then located on the site of the current bank's parking lot. In 1978, a new facility was erected behind the parking lot and the old structure razed.

In 1936, the “Hazel Green Station” was opened, primarily serving as a paying and receiving depot. It continued to evolve and became a full-service location in 1966.

In 1998, ATBancorp, formerly Amtrust, Inc., a family-owned bank holding company located in Dubuque, Iowa, purchased 100% of the stock of the Cuba City State Bank, retaining its Wisconsin state charter. In 2001, the bank was granted trust powers and also announced the expansion of services with a new full-service location in Lancaster. All three Wisconsin offices were united under the new name of American Bank & Trust–Wisconsin.

The year 2002 brought continued growth in the County and a new banking facility was built in Fennimore, Wisconsin to serve our clients to the north Then, in July 2006, American Bank opened an additional facility in the McGregor Plaza in Platteville. This newest branch served to combine the bank’s two Grant County market areas into one, which now spans the entire county. In its eighteen years since acquisition by ATBancorp, the bank has grown from $40 million to over $150 million in footings.

ATBancorp’s presence continues to grow in both Iowa and Wisconsin. Today ATBancorp is a three-bank holding company, encompassing American Bank & Trust in Wisconsin, American Trust & Savings Bank in Iowa, and United American Bank in San Mateo, CA. It presently has assets in excess of $1.5 billion and serves thirteen communities through eighteen banking facilities in Eastern and Central Iowa, Southwest Wisconsin, and San Mateo County.