Guided tours, field trips, and other non-formal learning experiences occur in a variety of settings such as museums, parks, civic buildings, and architectural landmarks for the purpose of educating the public. This study yielded four main findings. (1) Program educational goals were visitor awareness, positive affective experience, and advocacy. (2) Guides' intentions matched program goals, but varied in terms of discourse styles (expository, storytelling and interpretive), and in the level of encouraging social interaction. (3) Visitor learning aligned with, and exceeded, program goals. (4) Visitor learning related to expectation, delivery strategy of the guide, and opportunity for social interaction. Through the lens of Social Practice Theory and Activity Theory, this study addressed the overarching question: What do adult visitors learn through participating in a guide-mediated tour of a culturally significant setting? In order to understand the learning objectives within the community of practice and cultural tools at each setting, additional sub-questions addressed: (a) What are the educational goals of the guided tour as expressed by program managers and tour guide training documents? (b) What do the guides intend visitors learn? (c) How do the beliefs, practices and experience of the three participant types intersect to produce learning? This study examined tour programs at two sites: a Research Facility and a Public Library. Data were collected through document analysis of the official script and tour guidelines, observation of 11 one-hour-long guided tours, initial debriefings with 42 guided visitors and follow-up interviews with 12 of those visitors. The six guides who conducted the observed tours and the program manager at each site were also interviewed. This study builds on previous studies on non-formal learning by including program managers as study participants, rather than only recipients of data. Findings from this study can inform institutions which host non-formal education programs, and formal educators who incorporate guided tours as field trips into their curriculum. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]