In an attempt to engage primary-school students in a hands-on, real-world problem-solving context, a large urban district, a mathematics and science institute housed in a college of education, and a corporate sponsor in the southwest United States, joined forces to create a mathematics and science trail for fourth- and fifth-grade students. A mathematics and science trail is a series of locations at which students answer mathematics and science questions, connecting the environment to classroom learning. The "environment" is limitless because a trail can take place in a school, on school grounds, or within or beyond a community. This article describes the development and implementation of this ongoing project, the benefits of participation in a trail, and advice for those considering developing a trail. (Contains 6 figures).