List of Class I railroads

In the United States, railroads are designated as Class I, Class II, or Class III, according to size criteria first established by the Interstate Commerce Commission (ICC) in 1911, and now governed by the Surface Transportation Board (STB). The STB's current definition of a Class I railroad was set in 1992, that being any carrier earning annual revenue greater than $250 million. This has since been adjusted for inflation and most recently set to $504,803,294 in 2019.

This is a list of current and former Class I railroads in North America under the older criteria and the newer as well as today's much different post-railroad consolidation classifications.

Many of the more famous historical small railways possessing key trunk lines have been merged into one of today's behemoths.

Current Class I railroads

Today there are just five American owned Class I freight railroad companies and one passenger railroad company (Amtrak). The list also include two Canadian owned Class I freight railroads, both of which have trackage in the US.

Former Class I railroads

This list include very varied financial entities. From completely defunct companies, to operating companies with operations turned into investments, some hanging onto a corporate skeleton owning properties as holding companies, or have assigned their properties in mergers, bankruptcy or other legal acts (dissolution of the corporation) and finally others having become extinct—their works either torn up and hopefully recycled, or sold off to operating companies. This list does not indicate which is which.