The generous contributions of these community-minded, local businesses help to make the Mount Prospect Garage Sale Weekend possible.   Sponsorship info The Mount Prospect Garage Sale Weekend May 19, 20 & 21, 2017 Picking up your FREE Mount Prospect Garage Sale Map You will be able to pick up a FREE map of the participating homes Thursday through Sunday (May 18 - May 21, 2017) at the locations listed below.