Final answer:
The Southern Alliance achieved significant political power by 1890, bringing together over 2.5 million members, including 1 million Black members from the Colored Alliance.
Step-by-step explanation:
The Southern Alliance, which was a part of the larger Farmers' Alliance, achieved significant political power by 1890. The alliance brought together over 2.5 million members, including 1 million Black members from the Colored Alliance. While racial integration was not fully achieved, African Americans in the alliance recognized the benefits of political organization and a unified voice.