The most popular sign of the protest was the Shepard Fairey illustration of a woman wearing an American flag hijab, that I believe conflates misogyny and hate with American values of liberty.
Some of the most popular photos of the March we're American women wearing hijabs in solidarity.

Linda Sarsour is one of the women's march on Washington's main organizers. She literally argues for Sharia Law in the US on multiple posts on her Twitter account and the media and the left defend her. Sally Khon of CNN went so far as to claim that she was talking about "Sharia" (some vague spiritual notion) not "Sharia Law" (factually untrue, Linda uses the term Sharia Law and with reference to legal policy in America), and then went on to claim that even if Linda we're talking about Sharia Law as a political system, it's not that bad and we should be open to it.
There's a large movement in support of Linda called #imarchwithlinda.

It's all batshit insane in my opinion, but maybe I'm just an islamophobe.