The US state of Michigan abolished the death penalty in 1846, and according to Wikipedia, was the first English-speaking government in the world to do so; the death penalty has not been reinstated since then. On the other hand, the bordering state of Ohio is one of the most frequent users of capital punishment in the US.
So what led to Michigan's early abolition of capital punishment, as opposed to other states?
To make a long story short, it appears as though two things happened:
I guess the biggest takeaway here is that Michigan was very sparsely populated into the 1830s. Although it was rapidly settled after statehood (Wikipedia notes the population booming from 80,000 in 1837 to 212,000 in 1840), you would still have had a state government strongly influenced by the opinions of the few who had been there before incorporation. The above events took place in 1830 and before 1835 (the article cited above notes the deathbed confession having occurred in 1835), so it appears that when Michigan did become a state, there was a strong thread of "we are an anti-capital punishment state" already there.
Incidentally, Michigan was also not alone in abolishing the death penalty during this time frame. Wisconsin and Rhode Island also passed statutes which were, in a sense, even more stringent than Michigan's inasmuch as you could still be hanged there for treason. Elsewhere, moves were made at about this time to end mandatory death penalty sentences for many crimes (across the pond in England, the Bloody Code saw death penalty sentences for crimes such as grand larceny and pickpocketing, the latter of which created a queer situation in which a crowd that showed up at a pickpocket's hanging could themselves be visited by a pickpocket working his trade).
