Trails perform an essential function in protected lands by routing visitors along planned, sustainable surfaces. However, when visitors deviate from official trails in sufficient numbers, it can lead to the creation of social trails. These visitor-created pathways are not sustainably designed and can severely degrade both the stability and appearance of protected areas. A multitude of recreation motivations among visitors and a lack of resources among land management agencies have made the mitigation and closure of social trails a perennial concern. A sustainable, economical strategy that does not require the continual diversion of staff is needed to address social trails. In this study, two techniques that stand out in the research literature for their efficacy and practicality were tested on a social trail closure in South Mountain Park, a high-use, urban-proximate mountain park in Phoenix, AZ. A research design with additive treatments utilizing the site management technique known as trail mitigation, sometimes referred to as brushing in the literature, followed by theory-grounded signage incorporating injunctive-proscriptive wording, an attribution message, and a reasoning message targeting visitor behavioral beliefs, norms, and control was applied and assessed using unobtrusive observation. Both treatments reduced observed off-trail hiking from 75.4% to 0%, though traces of footsteps and attempts to re-open the trail revealed the existence of unobserved “entrenched” users. With entrenched users attempting to reopen the trail, trail mitigation represented an effective but vulnerable approach while the signage represented a long-lasting “hardened” approach that provides an educational message, management’s stance on the closure, and which might put social pressure on the entrenched user(s).