Final answer:
The Farmer's Alliance dissolved primarily due to internal conflicts and a decline in membership and influence, compounded by the rise of the Populist Party, which offered a more direct political solution to farmers' issues.
Step-by-step explanation:
The Farmer's Alliance dissolved primarily due to internal conflicts and disagreements, notably their exclusion of key segments of the agricultural population such as tenant farmers and African Americans. At its peak, the Alliance's membership grew to nearly 4 million, but the decision not to include large subgroups of farmers weakened its base. Moreover, these internal divisions and the inability to effectively represent and incorporate all farmers under its umbrella led to a decline in membership and influence.
The emergence of the Populist Party also played a significant role in the dissolution of the Farmers' Alliance. With the Alliance struggling to effect change on its own, many of its members joined the new political party, which promised to address the needs of farmers more directly and effectively. This shift in focus from organizing and educating in a union-like structure to direct political action signaled a transformation of the movement, effectively ending the Alliance's distinct role.