On December 9, the New York city council passed a bill to let non-citizen adult residents vote in elections for city office. Although fourteen other cities in the U.S. allow non-citizens to vote in at least some local elections, New York city is the first place to allow adult resident non-citizens to vote in a partisan election.
Although Mayor Bill de Blasio has not yet signed the bill, he has said that he will not veto it. Some city council members who oppose the idea plan to sue, arguing that the measure violates the New York state constitution, which is silent on that issue. Here is a Ballotpedia article about cities in the U.S. that allow non-citizens to vote. The article is very comprehensive and has information about the state constitutions of all states that relate to the issue.
Assuming the measure goes into effect, it will be interesting to see the voter enrollement statistics for non-citizens. Obviously there will need to be a separate voter registration list for non-citizens, because they still won’t be able to vote in federal and state elections, so the two lists must be kept separate.