Class I Railroads are the largest freight railroads in the United States, defined by their operating revenue. As of 2021, they must generate at least $505 million in annual revenue to qualify. These railroads play a crucial role in the transportation of goods across long distances, connecting various regions and industries. The Association of American Railroads (AAR) oversees the classification of railroads, which includes seven major Class I carriers like Union Pacific and BNSF Railway. These companies are vital for the economy, moving bulk commodities, intermodal containers, and other freight efficiently across the country.