This study aimed to determine how 33 urban 5th grade students' science conceptions changed during a place-based inquiry unit on watersheds. Research on watershed and place-based education was used as a framework to guide the teaching of the unit as well as the research study. A teacher-researcher designed the curriculum, taught the unit and conducted the research using qualitative data sources such as concept maps, science notebooks and interviews. Most students came to understand that their watershed was part of an urban environment where water drains from the surrounding land into a body of water. Thus, they began to understand how urban land use affects water quality. This study provides evidence for the use of place-based learning in developing students' knowledge of the "National Science Education Standards" (NRC, 1996) and watersheds. Implications of this study include the use of place-based learning in urban settings and the experiences needed for students to conceptualize watersheds. (Contains 5 tables and 3 figures.)