The Seaboard Coast Line was a short-lived conglomerate formed by the marriage of two of the Southeast’s largest and most profitable railroads, the Atlantic Coast Line and the Seaboard Air Line. Mergers, if planned and implemented correctly can save a railroad millions of dollars in the long term and this was the very reason behind the Seaboard Air Line and ACL discussing the option seriously, as early as the late 1950s. While the two companies were fierce competitors, similar to the Pennsylvania Railroad and New York Central who would also merge during the same period, the difference between the PRR/NYC and SAL/ACL partnerships was that the ACL and SAL spent many years planning their new system in an effort to ensure the marriage would go smoothly. As an independent carrier the Seaboard Coast Line would last a mere five years before joining under the banner of the Family Lines System, which would eventually disappear into the Seaboard System in 1982 (just ten more years later).
The first component of the Seaboard Coast Line was the Atlantic Coast Line, also known as the ACL or Coast Line, was synonymous with the South and served points from Richmond, Virginia to Florida and east to Birmingham, Alabama. The railroad was also very profitable being that it served direct north-south routes from Florida to Richmond. It also held one of the most unique paint schemes of any Class I of both its day, having a beautiful purple and silver livery with yellow trim. Remembered in the likes of the Southern Railway in later years the ACL was highly respected throughout most of its existence and like the Southern was blessed with excellent management and never faced any serious bankruptcy (and only entered receivership once during the Depression years of the early 1930s) threat
The Atlantic Coast Line began its life like many classic fallen flags, put together and shaped through a series of mergers with small railroads. Its earliest predecessor was the Richmond & Petersburg chartered in 1836, and after linking with the Petersburg Railroad the two made a through connection from Richmond to North Carolina. Throughout the 1800s there were numerous smaller lines that would go on to form the Atlantic Coast Line including the Wilmington & Weldon, Wilmington & Raleigh, and North Eastern which served points between South Carolina, North Carolina, and Virginia (including the ports of Wilmington, NC and Charleston, SC).
The ACL itself would begin to take shape when all of these railroads came under the control of William Walters, a Baltimore investor. In the late 1800s these railroads would come under the holding company of the Atlantic Coast Line Company. The railroad’s growth would not end with the 1800s. As each of its original lines were slowly merged into the holding company the ACL grew tremendously just after the turn of the century when it acquired the Plant System, a series of rail lines running throughout Georgia and Florida, and took control of the Louisville & Nashville, which served northeastern points from the ACL’s core system.
The rest of the ACL would come together in the 1920s when it gained control of the Atlanta, Birmingham & Coast giving it a link to western southeastern cities such as Birmingham, Alabama. In all, including its subsidiaries, the ACL was a giant system serving nearly every major southeastern market from Kentucky and Virginia, south to Alabama and Florida. Like a giant, and being well managed it earned substantial profits, calling on the L&N for help during the few short times when money was hard to come by.
The second component of the Seaboard Coast Line was the Seaboard Air Line, which is perhaps best remembered for being a somewhat smaller version of the Atlantic Coast Line as everywhere the ACL went so too did the SAL (and thus it is not surprising that the two would decide to merge in the late 1960s). This is not to say, however, that the SAL was an inferior road to the ACL, quite the contrary. The Seaboard held its own with its fiercest competitor and after managing to pull through troubled waters during the early years of its life, the railroad provided quality freight transportation to the Southeast.
Like all classic fallen flags, the SAL was derived over the years from several smaller lines which merged together or were later included under the Seaboard banner. The railroad itself has its beginnings dating back originally to the Portsmouth & Roanoke Rail Road, which was chartered in 1832 to connect Portsmouth, Virginia with Wheldon, Virginia, a town that sat along the banks of the Roanoke River (and was reorganized as the Seaboard & Roanoke in 1846). The other original components of the Seaboard included the Raleigh & Gaston Railroad (connecting Raleigh and Gaston, NC) and the Raleigh & Augusta Air-Line Railroad (connecting Raleigh and Hamlet, NC which would control both former lines by the 1870s).
Together these three lines formed the backbone of the later Seaboard Air Line system which first began to come together in the latter 19th century when John Robinson took control of the three and merged them as the Seaboard Air Line System. Throughout the rest of the 19th century and for the first part of the 20th century the Seaboard expanded north and south throughout the southeast reaching cities such as Richmond, Norfolk, Wilmington, Charleston, Atlanta, Savannah, and points west in Alabama (essentially everywhere rival ACL went!). The railroad also built one of the last major main lines in recent years when it completed an extension to Miami in 1927 (at its peak the railroad was a 4,000+ mile system).
The Seaboard’s transition into a major southeastern competitor began after it fell into receivership following the Great Depression (it emerged following WWII as the Seaboard Air Line Railroad). The railroad began to aggressively upgrade its system and reduce expenses by purchasing new locomotives (including new diesel-electrics) and equipment, and adding Centralized Traffic Control (CTC) to its single-track main lines.
After the ACL and SAL's merger in 1967 to form the Seaboard Coast Line the new railroad affiliated itself, along with a number of other railroads under the Family Lines System name. These railroads included the Louisville & Nashville and Clinchfield.
This arrangement lasted until 1982 upon which these railroads were formally merged as the Seaboard System that became part of CSX Transportation a few years later.
For more reading about the Seaboard Coast Line consider the book below from William Griffin. Seaboard Coast Line Family Lines Railroad 1967-1986: A CSX Predecessor gives a great general history of SCL up until its dissolution into CSX along with many excellent photographs which complement the book. If you have an interest in the SCL you will likely find this book quite interesting.