You can register at your county courthouse, at some city offices (such as the Carbondale City Hall), or at an Illinois drivers license facility (IF you are conducting other business there).

You need to show two forms of identification, with one showing your current residence address — such as a driver's license or a recent utility bill.

The only time you cannot register is from 28 days before any election until 3 days after the election.

In Illinois, you do not indicate a political party when you register — you are not registered "as" a Green, for example.  In a primary election, you are offered a choice among the ballots of the established parties, and — since November 7, 2006 — the Green Party is one of those options.