The coat of arms lent by Erhard Vöhlin in the year 1530 shows an upright standing lion in red, covered by a black bar with three "P"s in silver capital letters.

The trade house of the Vöhlin (1520-1757), a patrician family from Memmingen, heavily influenced the history of Illertissen.

In the 18th century, the financial bankruptcy of the Vöhlin ended, and led to the sale of their rule to the Bavarian elector Maximilian III.

An important development in the agrarian market was the opening of the Ulm - Oberstdorf railway line in 1861/62, the so-called Illertalbahn.

Three years after the war, the currency reorganization and the free-market economy led to an upswing like never before, and new industries emerged.

In 1971, Betlinshausen was incorporated, and Au, Jedesheim and Tiefenbach were added in 1978, as part of a regional reorganization.