The Opportunities for Enhancing Diversity in the Geosciences (OEDG) program, operational between the years 2001 and 2013, was a signature effort by the National Science Foundation's Directorate for Geosciences (NSF/GEO) to invest in broadening participation of historically underrepresented populations in geoscience education programs and careers. Nearly 200 individual grants totaling more than $50 million in federal funding were provided by the OEDG program to a diverse portfolio of projects that targeted a variety of audiences and age levels. Project-level evaluation and assessment has demonstrated that most OEDG-supported projects achieved successful outcomes and impacts, according to their design. Integrating geoscience content with meaningful cultural context and relevance, authentic research experiences, cohort-based mentoring, direct financial support, and minority--majority institution collaborations have been found to be some of the most fruitful approaches for engaging, recruiting, and retaining minorities in geoscience pathways. Synthesis of the outcomes and impacts attained through the entire OEDG portfolio by a third-party evaluator demonstrated that the 10-year program achieved its primary goals. Despite these individual successes, progress in making the professional geoscience workforce more diverse has continued to be slow, especially at the doctoral level. Although OEDG research has shown what types of strategies can be effective for engaging and retaining diverse students in the pipeline, many require resources that make it challenging to bring such efforts to scale. Better progress can be achieved if a larger community of geoscientists is engaged in advocating for and fostering diversity within the geosciences using the most cost-effective approaches. Significant and sustainable change will only be realized, however, when the levers that drive behavior in the educational and professional systems of the geosciences are tuned so that diversity is recognized as a core value and fundamental feature of scientific excellence and integrity.