The term "4-4-0" refers to a type of steam locomotive configuration characterized by its wheel arrangement. In this setup, the locomotive has four leading wheels, four driving wheels, and no trailing wheels. This design was popular in the United States during the late 19th and early 20th centuries, primarily for passenger and freight services. The 4-4-0 locomotives were known for their versatility and speed, making them suitable for various rail lines. They played a significant role in the expansion of the American railroad system, contributing to the growth of commerce and travel during that era.