In 1967, the state capital of Mainz made the artworks and objects in its art gallery and antiquities collection available on permanent loan for the founding of what is now the Mainz State Museum, then known as the Middle Rhine State Museum Mainz. The objects are still in the State Museum today and form the core of the exhibits on display and in storage there.

At the same time, the cultural office of the state capital began to bring together new works of art in an art collection in the Eisenturm. To this day, the art collection chronicles the visual arts in Mainz and includes works from various fields of artistic activity in the city. Through purchases, gifts, and donations, the collection has grown continuously and now comprises almost 1,500 works by artists from Mainz, the region, and partner cities.