My friend Branigan Robertson made the below video on raising effective workplace complaints while avoiding retaliation. He also writes about it here.
All of these tips are great, and they apply equally to Illinois employees. Tip number six is especially important: send a written complaint. Unfortunately, potential clients tell me all too often that they only complained about illegal conduct in-person or on the phone. Unfortunately, judges give these non-written complaints very little weight. Even more unfortunate, individuals who still work for the employer often have a different “memory” than you. Thus, if you make any complaint, it needs to be in writing. A simple email will do the trick, and you can print out a copy of the email for your records.
In the unfortunate event you need to make a workplace complaint, make sure to follow these tips. When in doubt, contact an experienced employment attorney.

a case to decide if employers with fewer than twenty employees can be considered “employers” if they are a state or political subdivision of a state. It is unclear if the political entity must 



hire or to discharge any individual, or otherwise to discriminate against any individual … because of such individual’s race, color, religion, sex, or national origin.” 42 U.S.C. § 2000e-2. Thus, the question is whether discrimination based on sexual orientation is considered discrimination because of an individual’s sex. The Equal Employment Opportunity Commission 
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