Results from a Sunday referendum showed that 83.2 percent of voters in Hesse, home to finance hub Frankfurt, were in favour of changing the state constitution written in 1946 that allowed capital punishment.
Just three years later, Germany's new post-war constitution, known as the “Basic Law of 1949”, formally abolished the death penalty.
As it overrides state laws, it essentially made Article 21 of Hesse's constitution, which states: “For especially severe crimes, the sentence can be death,” irrelevant.
But, in a legal quirk, Hesse never formally amended its local legal code, leaving it the last German state where capital punishment was still on the books.
A referendum was held because Hesse is the only German state where constitutional changes have to be put to the people.
Between 1946 and 1949 Hessian courts twice handed down death sentences, according to regional news site Hessenschau, although both were converted to prison terms.
The first accused was a man convicted of murdering his wife.
The other was Nazi doctor Hans-Bodo Gorgass, found guilty of killing at least 1,000 people as part of Hitler's “euthanasia” programme.
Hesse now has “a modern constitution adapted to the realities of the 21st century,” said state premier Volkier Bouffier, a close ally of Chancellor Angela Merkel.
In Europe, only Belarus maintains the death penalty in both law and practice, while 102 countries worldwide have abolished it.
The referendum in Hesse coincided with a regional vote that rocked the country the next day, when Merkel reacted to heavy losses for her centre-right CDU by announcing she would step down as party leader in December.
She added that she intends to stay on as chancellor until her term ends in 2021.