Chartered in Kentucky in 1850, the L&N was one of the South’s early railroads and one of only a very few to grow into a major system without a name change. The name survived into the 1980s, when it was abandoned as part of the organization of CSX.
L&N's 185-mile main line between Louisville, Ky. and Nashville, Tenn. opened in 1859. It became the last link in a chain of southern antebellum railroads connecting the Ohio River with the Atlantic by way of Louisville, Nashville, Chattanooga, Atlanta, Augusta, and Charleston.
In 1880 L&N acquired 55% of the stock of the Nashville, Chattanooga & St. Louis Railway, which had opened a line from Nashville to Chattanooga in early 1854.
In 1881, the L&N and the Central of Georgia jointly leased the Georgia Railroad.
In 1889 the company reported operating 2,614 miles of railroad with 436 locomotives, 339 passenger cars, and 12,534 freight and miscellaneous cars.
In 1890 NC&St.L leased the Western & Atlantic from the State of Georgia, giving it, and the L&N, a major presence in the northwestern section of the Peach State.
L&N came close to entering southwestern Georgia but its Pensacola & Atlantic Railroad subsidiary stopped at Chattahoochee, Florida, just short of the state line. Here, at a point called River Junction, the P&A/L&N connected with the Savannah, Florida & Western (later Atlantic Coast Line) route to Climax, Georgia.
Atlantic Coast Line gained control of L&N in 1902 by purchasing all of the L&N stock owned by financier J.P. Morgan, who had managed to acquire a majority interest in the company. L&N continued to operate independently, however, with no significant change in management.
L&N acquired the Atlanta, Knoxville and Northern Railway in 1902. This route between Marietta, Georgia and Etowah, Tennessee was often called the "Hook and Eye Line" because of a pair of unusual engineering features along the route. The "Hook" was a tight double reverse curve at Tate Mountain, Georgia between Whitestone and Talking Rock. The "Eye" is an 8000-foot loop that climbs Bald Mountain near Farner, Tennessee, encircling it almost twice before crossing back over itself and turning south towards Georgia. It was built in 1898 to replace a set of switchbacks.
L&N constructed the line between Cartersville, Ga. and Etowah, Tenn. in 1906, primarily to bypass the mountainous Hook & Eye Line. The latter became known as the Etowah Old Line.
As part of the AK&N acquisition, L&N gained a newly constructed belt line on the west side of Atlanta. Running from Howells on the northeast to the Atlanta Belt Railway south of the city, it allowed trains to access L&N's affiliate Georgia Railroad without passing through the center of downtown. (See Atlanta Belt Line.)
NC&St.L was merged into L&N in 1957.
In 1967, L&N’s parent Atlantic Coast Line merged with Seaboard Air Line Railroad to form Seaboard Coast Line Railroad. L&N meanwhile continued its separate existence. From 1972 until the early 1980s, the railroad also used the marketing name Family Lines System jointly with SCL, Georgia Railroad, Clinchfield Railroad, Atlanta & West Point Rail Road, and Western Railway of Alabama (the last two also operating under the nickname West Point Route). This confusing arrangement ended when SCL and Chessie System merged in 1980 to form CSX Corporation.