The SCL was created on July 1, 1967 by the merger of the Seaboard Air Line Railroad and the Atlantic Coast Line Railroad. Combining 4,123 miles of Seaboard tracks with 5,743 miles of ACL rails, the new railroad's length equalled the distance from Key West to Alaska to San Diego and back to Key West. Unfortunately, SCL's mileage consisted of mostly parallel lines limited to six southeastern coastal states. That fact would ultimately lead to extensive abandonment of lines in Georgia and elsewhere.
Serious merger talks between the two began in 1957, or earlier. In September of the following year, Thomas Rice of the ACL and John W. Smith of the Seaboard made a joint announcement of preliminary plans to merge. It would not be until late 1963, however, that the Interstate Commerce Commission voted to approve the marriage, and not until April 1967 that the U.S. Supreme Court ended over three years of federal court battles initiated by merger opponents.
In 1972, Seaboard Coast Line became part of the “Family Lines System,” a marketing name used jointly by SCL and the Louisville & Nashville Railroad, along with their subsidiaries Georgia Railroad, Clinchfield Railroad, Atlanta & West Point Railroad, and Western Railway of Alabama (the last two operating under the marketing name West Point Route). The name was used from 1972 until the early 1980s.