Final answer:
Billboard changed its "race record" chart to "rhythm and blues" in the 1940s, specifically in 1949, to reflect a more inclusive and modern approach to the music of African American artists.
Step-by-step explanation:
Billboard modified its "race record" chart to "rhythm and blues" in the 1940s. Specifically, this change occurred in 1949, marking a significant shift in the music industry's recognition and categorization of African American music. The term "race records" was deemed outdated and offensive, and the new category of rhythm and blues was introduced to provide a more inclusive and respectful terminology for the music predominantly made by African American artists during that era. Billboard's rhythm and blues chart would go on to track the popularity of such music and became an important barometer for the emergence of new styles and artists, including rock and roll pioneers like Bill Haley and His Comets and the electrifying performances of artists such as Chuck Berry.