The Little Miami Railroad was a railway of southwestern Ohio, running from the eastern side of Cincinnati to Springfield, Ohio. By merging with the Columbus and Xenia Railroad in 1853, it created the first through-rail route from the important manufacturing city of Cincinnati to the state capital, Columbus. In this period, railroads were important for creating connections between the important waterways of the Great Lakes and the Ohio River, which were major transportation routes for products to other markets.
The LMRR's importance declined later in the 19th century, after three major railroads from the East built lines across the Allegheny Mountains and established east–west transportation systems through the state. It continued independent operations until 1981, after being absorbed by Conrail during the period of extensive railroad restructuring in the late 20th century.