A more thorough explanation:

The Elkins Act was a law passed by the federal government in 1903. It made the Interstate Commerce Act stronger by making it illegal for big transportation companies to receive special treatment or discounts.

For example, if a railroad company was giving a discount to a big customer, they would have to give that same discount to all customers. This prevented big companies from getting an unfair advantage over smaller ones.

The Elkins Act helped to promote fair competition in the transportation industry and protect smaller businesses from being pushed out by larger ones.