Anyone who spends a lot of time on public lands in the U.S. is likely to encounter traces intentionally left by modern visitors, such as rock cairns, painted “kindness stones,” or even fairy houses. For some people, including most park managers, these traces are a violation of the Leave No Trace ethic. But, others find them charming and question what real harm they cause. This talk offers an anthropological analysis of what the practice of leaving traces is all about and why people have such different views, drawing on philosophical understandings of wilderness, cultural heritage studies, and archaeology of the contemporary. The presenters focus in particular on two parks known for their Indigenous stories, Mesa Verde National Park in Colorado and Machimoodus State Park in Connecticut.