Older than the country
The idea that a jury can refuse to convict is older than the United States. It comes from the English trial, where twelve people from the community decided whether their neighbour was guilty, and where, more than once, a jury refused to convict a person the Crown wanted convicted. Those refusals are part of why the jury came to be seen as a protection for the person on trial, and not only as a way of finding facts.
The American colonies inherited that trial, and that view of it. Colonial juries acquitted people charged under laws the community did not accept, and the memory of those verdicts was fresh when the new states wrote their first constitutions.
The founding era
The first American constitutions, state and federal, promised a trial by jury in criminal cases. Some went further and spoke to what the jury decides. A few said, in so many words, that the jury judges the law as well as the facts. Others said only that the right to a jury shall remain as it was. Those sentences are still on the books, and several state constitutions carry them today. Which states, and in what words, is in each state's chapter.
In that era it was common for a judge to tell the jury that it could decide the law for itself. That practice did not last.
The long turn toward the judge
Over the course of the nineteenth century, American courts moved to a different rule: the judge states the law, the jury finds the facts and applies the law as the judge gives it. By the end of that century the move was largely complete in the federal courts, and most states had followed or were following. The standard instruction most jurisdictions read today is the descendant of that turn. Of the 52 jurisdictions this guide covers, 49 have one.
What the turn did not do is take away the jury's power to acquit. It changed what jurors are told, not what a not-guilty verdict does. That gap, between the instruction and the power, is the subject of the rest of Foundations.
Why the past still matters in your state
The history is not uniform, and neither is what it left behind. A state that wrote "the jury shall be the judges of law and fact" into its constitution two centuries ago may still have those words today, next to a modern instruction that says the opposite. Another state never wrote them at all. Of the 52 constitutions and charters, 23 address the jury's role in deciding the law and 29 do not.
Which of those your state is, what its founding text says, and how its courts read that text now, is in its chapter, with the citation for each.