Catcalls of NYC is a grassroots initiative that uses public chalk art to raise awareness about gender-based street harassment. We solicit stories of harassment and their locations in NYC, write out the comments in chalk word-for-word with the #stopstreetharassment, and post the images on social media. The goal is to spur dialogue, provide a platform for story sharing, and promote cultural change. Since I started Catcalls of NYC in March 2016, it has inspired over 150 young activists around the world to start "Catcalls of" sites in their cities. Now, we make up Chalk Back, a global youth-led movement against gender-based harassment. Local sites create bold street art, organize community events and provide leadership on issues of harassment.