At our small liberal arts college, we recently introduced a field trip-based course as a requirement for all first-year science majors. This course, entitled "The Urban Ecosystem," explores various aspects of science and technology using our city (New York) as a case study. Beyond its curricular content, the Urban Ecosystem course has two pragmatic goals: (a) to promote persistence in STEM, and (b) to help students adapt to college life on our urban campus. In this study, we seek to understand the impact of various innovative aspects of the course on students' adaptation to a college STEM program. We describe how each course component addresses a key factor associated with STEM attrition, and we report 2 years of survey data from course participants to assess the effectiveness of our methods. We find that students benefit particularly from the social bonding aspects of the course, and we link the experience of the course with record second-year retention among our life science majors. Ultimately, longer term retention data will allow examination of the broader impact of an interactive first-year experience course on undergraduate STEM persistence.