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