Born at Eichtersheim (now Angelbachtal in Baden-Württemberg), the son of a revenue official, he studied law at Heidelberg university with the intention of becoming a lawyer. In Heidelberg he became a member of the Corps Rhenania. On entering the Second Chamber of Baden in 1842, he at once began to take part in the opposition against the government, which assumed a more and more openly radical character, and in the course of which his talents as an agitator and his personal charm won him wide popularity and influence.

A speech, denouncing the projected incorporation of Schleswig and Holstein with Denmark, delivered in the Chamber of Baden on February 6, 1845, spread his fame beyond the limits of his own state, and his popularity was increased by his expulsion from Prussia on the occasion of a journey to Stettin. After the death of his more moderate - minded friend Adolf Sander (March 9, 1845), Hecker's tone towards the government became more and more bitter. In spite of the shallowness of his culture and his extremely weak character, he enjoyed an ever - increasing popularity. Even before the outbreak of the revolution, he included socialist claims in his programme.

In 1847 he was temporarily occupied with ideas of emigration, and with this object made a journey to Algiers, but returned to Baden and resumed his former position as the radical champion of popular rights, later becoming president of the Volksverein, where he was destined to fall still further under the influence of the agitator Gustav von Struve. In conjunction with Struve he drew up the radical programme carried at the great Liberal meeting held at Offenburg on September 12, 1847 (entitled Thirteen Claims put forward by the People of Baden). In addition to the Offenburg programme, the Sturm petition of March 1, 1848 attempted to extort from the government the most far-reaching concessions. But it was in vain that on becoming a deputy Hecker endeavoured to carry out its impracticable provisions. He had to yield to the more moderate majority, but on this account was driven still further towards the Left. The proof lies in the new Offenburg demands of March 19, and in the resolution moved by Hecker in the preliminary Frankfurt Parliament that Germany should be declared a republic. But neither in Baden nor Frankfurt did he at any time gain his point.

This double failure, combined with various energetic measures of the government, which were indirectly aimed at him (e.g. the arrest of the editor of the Constanzer Seeblatt, a friend of Hecker's, in Karlsruhe station on April 8), inspired Hecker with the idea of an armed rising under pretext of the foundation of the German republic. The 9th to the 11th of April were secretly spent in preliminaries of what would be known as the Hecker Uprising. On April 12, Hecker and Struve sent a proclamation to the inhabitants of the Seekreis and of the Black Forest to summon the people who could bear arms to Donaueschingen at mid-day on the 14th, with arms, ammunition and provisions for six days. They expected 70,000 men, but only a few thousand appeared.

The grand - ducal government of the Seekreis was dissolved, and Hecker gradually gained reinforcements. But friendly advisers also joined him, pointing out the risks of his undertaking. Hecker, however, was not at all ready to listen to them. On the contrary, he added to violence an absurd defiance, and offered an amnesty to the German princes on condition of their retiring within fourteen days into private life. The troops of Baden and Hesse marched against him, under the command of General Friedrich von Gagern, and on April 20 they met near Kandern, where, although Gagern was killed, Hecker was completely defeated.

During the second rising in Baden in the spring of 1849 he again made efforts to obtain a footing in his own state, but without success. He only came as far as Strassburg, but had to retreat before the victories of the Prussian troops over the Baden insurgents.

Hecker provided a foreword to the German translation of Thomas Paine's The Rights of Man which was published in Leipzig in 1851.

Like many of the revolutionaries of that period, Hecker retired to Switzerland. Although he was again elected to the Chamber of Baden, the government, no longer willing to respect his immunity as a deputy, refused its ratification. On this account Hecker resolved in September 1848 to emigrate to North America like many other "Forty - Eighters", and obtained possession of a farm near Belleville in the state of Illinois.

He won some distinction during the Civil War as the colonel of a regiment that he had raised on the Federal side in 1861 (the 24th Illinois Infantry Regiment). However, his harsh strict discipline style upset some of the other officers; he resigned and the unit was dissolved. In October 1862, he became colonel of the 82nd Illinois Infantry Regiment and served in the eastern campaigns, being wounded at Chancellorsville on May 2, 1863. He later served at the Battle of Missionary Ridge and the capturing of Chattanooga and Knoxville.

Afterwards, he returned to his farm in Illinois. He had strong anti-slavery views and did writing and speaking for the German - speaking community in connection with the Presidential campaigns of John Frémont and Abraham Lincoln.

It was with great joy that he heard of the union of Germany brought about by the victory over France in 1870 - 71. It was then that he gave his famous address at St Louis, in which he gave animated expression to the enthusiasm of the German Americans for their newly united fatherland. After the war, he became more and more involved in the German language press and Republican Party activities. He received a less favourable impression when he visited Germany in 1873 for criticizing lack of individual rights and the size of government in the new German government organization. He died at his farm in Summerfield, Illinois, on March 24, 1881.

Hecker was always very much a favourite with all the German democrats. The song and the hat named after him (a broad slouch hat with a feather) became famous as the symbols of the middle classes in revolt. In America he won great esteem, not only on political grounds but also for his personal qualities.