Final answer:
The Republican Party and the Populist Party opposed the power of the railroad in the late 19th century.
Step-by-step explanation:
The two political groups that opposed the power of the railroad in the late 19th century were the Republican Party and the Populist Party.
The Republican Party emerged as a political coalition in 1854, bringing together various groups opposed to the extension of slavery. While the party's main focus was on issues related to slavery, it also supported regulation of the railroad industry to prevent monopolistic practices.
The Populist Party, also known as the People's Party, was formed in the 1890s and gained support from farmers and workers who were facing economic challenges. The party advocated for the regulation of railroads and other industries to protect the interests of the common people.