The town is located in the district of Heidenheim at the eastern edge of the Swabian Alb, about 30 kilometers northeast of Ulm on the Brenz River.

The first documentary evidence of the town was contained in a chronicle of the monastery of Peterhausen that reported on the death in battle in 1078 of margrave Diepold II von Vohburg, lord of Giengen.

Yet, Giengen was to be one of the 50 Free Imperial Cities that were to survive the Thirty Years' War and the Peace of Westphalia and continue as quasi-sovereign entities until 1802-03.

Like almost all the other Imperial Cities, Giengen was profoundly transformed by the Protestant Reformation, which made its way into the city-states before it did into the secular and ecclesiastical principalities of the Empire.

Even before the advent of the Reformation, there had been much discontent against the pervasive influence of the Church, particularly in the Free Imperial Cities that, while largely independent politically, had to contend with the control of the Church in religious matters such as tithes, ecclesiastical tribunals, etc., not counting the fact that religious property and the clergy, both secular and regular, were largely exempted from taxation and civic control.

Therefore, a final break with Rome and the local bishop—in the case of Giengen, the Bishop of Augsburg—meant the end of a severe irritant and a significant increase in the political reach of the new Protestant cities and princes who, from then on, would have full control over the reformed clergy, tithes and religious regulations and foundations.

Not much happened in the sleepy city: the belfry of St. Georg’s church’s was rebuilt after a fire and a new baptismal font was donated by a prominent citizen; an organ-making shop opened business; one Jakob Osswald and his daughter are beheaded for “incestua cum filia”.

A 1734 survey showed that there were "130 horses, 150 heads of cattle, many pigs and 1,000 sheep" in the tiny Free Imperial City, which had a distinct rural character.