The mountain at a ford over the Eder north of the Burgwald range was for a long time a fortified place, playing an especially important role under the Franks in the Saxon Wars.

[citation needed] Frankenberg lies between the Burgwald range in the south and the Breite Struth (hills) in the northwest, where the river Nemphe empties into the Eder.

‡ Population figures as at 2012 At the foot of the mountain on which the town of Frankenberg was built crossed two old military and commercial roads.

From the area of the lower Main, from the Burgwald range, came the Weinstraße ("Wine Road"), crossing the Eder through a ford and then going on through the heights on the river's left bank to Westphalia.

After the Hesse area had been swallowed up into the Frankish domains about the year 500, the well-defended mountain became involved in the quarrels of heightened military importance with the Saxons who lived north of the Eder.

As the number of Saxon incursions nevertheless rose in the early 8th century, Charles Martel had strong defences built, ensuring their efficacy by maintaining a constant presence there.

Since the Frankenberg had passed to the Landgraves in 1122 and lay in the Vogtei of the Vögte von Keseberg, he chose, right in the middle of the Mainz county of Battenberg, on the boundary between the court regions of Röddenau and Geismar, to build a castle, and furthermore a town, disregarding all of the local lords' objections.

On the uppermost peak of the mountain, which fell away steeply on three sides, appeared the castle, commanding the whole middle Eder Valley.

Frankenberg buyers and sellers broadly fostered trade links, as witnessed not only by the weekly markets, but also by the four yearly fairs.

It rose along the Siegener Straße (a commercial road), even having its own administration, although it was still under the Old Town's church and court, and had no marketplace of its own.

Only in the 16th century was there once again an Amt of Frankenberg under which were united not only the town but also Rodenbach farm and the Wiesenfeld wine cellars.

After 1526, as was true throughout Hesse, the Reformation was introduced into Frankenberg by the preachers Ludwig Stippius and Caspar Tholde.

Under Napoleonic rule (1806 to 1813), Frankenberg was home to the seat of a canton in the department of Werra in the Kingdom of Westphalia.

In 1890, the Marburg-Frankenberg line was opened, and the Brothers Thonet from Vienna furthermore set up a chair-making factory near the railway station making use of the wealth of wood in the area.

With this turbine and a naturally aspirated gas engine (60 horsepower), direct current was generated for Frankenberg's first electric light.

As part of the electrification of North Hesse, alternating current power supplies were ensured with PreussenElektra's overland cables in 1921.

Even a town expansion of 144 ha east of the cemetery, as recommended in 1914 in a report about the Gau of Frankenberg by the Research Body for German Housing Business (Forschungsstätte für die Deutsche Siedlungsgesellschaft) at the Reichsherrnstättenamt, was never undertaken.

As the money lost its worth and the attendant economic downfall set in, there came a new wave of emigration from the town, especially overseas.

When the inflation ended in autumn of 1923, bringing with it an upswing in the economy, this was expressed in, among other ways, the Stoelcker chair factory setting up shop in town in 1925.

In the face of rising joblessness and social need, the NSDAP's propaganda was finding fertile ground here, as it was throughout the district, by the end of the 1920s, which was reflected in election results.

After Hitler seized power in January 1933, Frankenberg town council gave several places new names: the Steingasse ("Stone Lane") became Adolf-Hitler-Straße, Röddenauer Straße became Hermann-Göring-Straße, and the Untermarkt ("Lower Market") became Hindenburg-Platz, and the people, above all the youth, were infected with the Nazi ideology.

Worst affected by all this were Frankenberg's Jewish townsfolk, who, already having had to deal with discrimination and harassment for a long time, were systematically persecuted, stripped of their rights, and in the end, murdered.

At least eight Jews from Frankenberg and three from the outlying centre of Röddenau lost their lives to the Nazis' racial madness.

Since 1988, a memorial plaque at the town hall has recalled Frankenberg's Jewish community and Holocaust victims.

In August 1944, a Wehrmacht field hospital was moved from Grodno to Frankenberg and housed at the town's two schools and at the Amt court.

With the stream of refugees after the Second World War, Frankenberg's population rose sharply by two thousand, requiring that the town's building area be expanded.

Late in the 1970s, there came into being on the Kegelberg a workshop for those with disabilities and an integrative kindergarten sponsored by the Lebenshilfe-Werk ("Assisted Daily Living Works") On the floodplain in the 1960s an industrial park opened up – and has been expanded – in which a few sizeable new businesses have been able to establish themselves, strengthening Frankenberg's economic power and improving its economic structure.

Established in Frankenberg are, among others, the famous furniture factory of the Brothers Thonet, a plant belonging to the injection moulding firm Hettich and the Bundeswehr's Electronic Warfare Battalion (Bataillon Elektronische Kampfführung) 932.

This ten-year programme sought to choose two midsize towns in Hesse, and Frankenberg was chosen from a field of 33 candidates.

With the "Family town with future" model project, the state of Hesse would like to test whether, and if so with what success, municipal measures can have a positive influence on demographic development.