In Whyte notation, the 4-4-0 wheel arrangement is called American.
The notation counts wheels from front to rear: four leading wheels, four coupled driving wheels, and no trailing wheels. The four leading wheels were usually arranged in a two-axle guiding truck, while the four larger driving wheels supplied traction. “American” became the best-known name for this arrangement in North American railroad practice; “Eight-Wheeler” was another name.
The type emerged in the 1830s and became extraordinarily common in the United States. Its leading truck improved stability and allowed locomotives to negotiate curves more effectively than earlier designs, while the two driving axles provided useful pulling power for the trains of the era.
The name does not mean every 4-4-0 was built in America. British railways also operated locomotives with the arrangement, and the same wheel pattern can be identified by other classification systems, such as the UIC designation 2′B. “Pacific” means 4-6-2, “Mogul” means 2-6-0, and “Atlantic” means 4-4-2.