Here's the list via NPR:

The states joining New York State Attorney General Eric Schneiderman's lawsuit filed Tuesday in Manhattan federal court are: Connecticut, Delaware, Illinois, Iowa, Maryland, Massachusetts, Minnesota, New Jersey, New Mexico, North Carolina, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia, Washington. The cities are: Washington, D.C., Chicago, New York, Philadelphia, Providence, Seattle, and San Francisco, plus the United States Conference of Mayors, a bipartisan group.

I figured at least a few Republican-controlled states would join the lawsuit against the decision and more than a few are in the mix. The governors of Iowa, Maryland, Illinois, New Mexico, and Vermont are Republicans although they may not necessarily agree with the actions of their respective attorneys general. If any of them strongly disagree, however, they haven't screeched about it yet.

The lawsuit contends that adding a citizenship question will prevent the federal government from living up to its "constitutional responsibility" of counting every person in the United States. The Trump regime is probably going to say it won't lower response rates, but we already know Commerce Secretary Wilbur Ross overruled careers officials at the census bureau who say it will.

This lawsuit falls under the jurisdiction of the Second Circuit Court of Appeals based in New York City.