Between 1865 and 1900 an issue that dominated national politics in the united states was

The rise of big businesses is the answer 

Many of the issues dealt with by the courts during this time frame had to do with large companies creating monopolies. Many people were sued over their practices. Today we have Ford, because of a lawsuit that allowed him to enter the automotive industry. Rockefeller was also taken down over his oil monopoly.

Hope that helps.