The purpose of this study was to determine the effectiveness of a teacher professional development (PD) program as measured by the extent that participants have continued to use lessons and materials up to three years after the PD experience. The PD was delivered online and structured by five key characteristics of effective PD. A causal-comparative analysis of 65 participants of the Food, Land, and People (FLP) PD was performed using a sustained implementation scale (SIS). Participants completed an online survey answering certain demographic variables and indicating the number of lessons and activities they had used from the FLP PD. The SIS model was used to create weighted FLP use scores and compare participants within each group. Results suggest participants continued to use PD materials up to three years after the PD. Further analysis found significance between SIS scores and years of teaching experience. Results suggest that the FLP PD program was effective in obtaining long-term continued use of materials.