The two major types of anti-competitive activities were practiced by railroads in the United States between 1865 and 1904. They were charging very high freight rates and the larger railroads would buy out the smaller railroads to expand their geographic reach or eliminate a pesky competitor.
During the 1900 to 1923 period, the US Government fought three major battles to prevent railroad mergers. 1) James T Hill owned the Great Northern railroad. In 1895, he acquired control of the financially weak Northern Pacific and in 1898, both the Northern Pacific and Great Northern bought 98 percent of the stock of the older and larger Chicago Burlington & Quincy railroad. Hill formed the Northern Securities Corporation and tried to merge his three major railroads into one company. This merger was prevented by the Federal government in one of their first major victories in the area of trust busting. 2) H.H. Harriman wanted to merge the Union Pacific and the Southern Pacific into one very large railroad. Harriman died in 1909 and the Interstate Commerce Commission tried to divorce the UP and SP. That case dragged on until 1923, because the Union Pacific wanted to keep what was the original Central Pacific and own the route between Ogden Utah and the San Francisco Bay area. The Southern Pacific did not want to lose this route and eventually they prevailed. 3) The New York Central & Hudson River Railroad wanted to merge with the Lake Shore & Michigan Southern, a railroad that the Vanderbilts already owned. That merger was finally approved in 1914, provided the Vanderbilts and the New York Central divested themselves of one of the three following railroads. The Chicago, Cleveland, Cincinnati & St Louis railroad (also known as the Big 4), the Michigan Central or the New York, Chicago & St. Louis railroad. The New York Central sold the NYC&StL to the Van Swerigan brothers, because it was the smallest and weakest of the three railroads the ICC wanted the New York Central to divest. All three of these cases showed the ICC had strong teeth and the ICC was not very likely to allow railroad mergers to take place, between 1900 and 1960.
The ICC also developed a very strong system rate regulation, through the passage of a series of Acts in the Teddy Roosevelt administration. The ICC could set maximum freight rates, minimum freight rates, hold lengthy hearings to determine if any railroad mergers were in the public interest and mandated passenger ticket costs and how many passenger trains the railroads were required to run on their routes.
The railroads had it coming. During the Gilded Age there was no viable competition from other transportation modes, weak railroad worker unions and limited safety regulations. The railroads gouged their customers so badly, they turned the Fraternal Order of Husbandry (the Grange) into a major political entity and pressure group. At first, the Grange tried to get the individual states to regulate rates, but the Railroads, which were the largest and wealthiest corporations in the Gilded age, were able to get these state laws overturned, citing the Commerce Clause of the Constitution. That was a short sighted policy and basically invited the US Congress to set up the ICC and give it stronger and stronger powers. Important acts of Congress that curbed the power of the railroads were: The Railway Safety Appliance Act of 1893, The Mann Act of 1904 that set maximum freight rates, The Elkins Act of 1907 that set minimum freight rates, and the Panama Canal Act of 1912 that prevented railroads from owning steam ship companies.
Source: "Contemporary Transportation" by Donald Wood and James Johnson.