1955 Louisiana Highway renumbering

In 1955, Louisiana passed a law that undertook a comprehensive revision to the state highway classification and numbering system. The new system designated roads by importance to travel patterns and rectified the previous numbering system under new unified designations.

Highway numbers in Louisiana first appeared in 1921, per Act 95 of the 1921 Special Session of the Louisiana Legislature. Routes 1 through 98 were defined that year. These first 98 routes remained consistent throughout the pre-1955 era. The lowest numbered routes seem to have followed major auto trails; for instance, LA 1 was the Jefferson Highway, LA 2 was the Old Spanish Trail, etc. The remainder of the numbering system seemed to work on a lower-number, higher-order principle, with some clustering; for instance, LA 61 and 62 both existed in St. Bernard Parish. When US highways were added in 1926, the US designations were simply overlaid over the preexisting state route (SR) designations in a method similar to modern Georgia (the state route was included in signage as well).

Other routes were added as time went on, numbered in consecutive fashion, starting with LA 99 in 1924. By 1926 there were 162 defined routes; by 1929, 490. The number of routes increased precipitously during the Huey Long era, with 1325 routes defined by 1930 and more to come. A few routes were given "half" numbers, such as LA 99½ and LA 1315½, for reasons perhaps related to numerical duplications in the official legal descriptions of the routes. (LA 99½, which had been jokingly referred to as "the left lane of 100," was redesignated in the pre-1955 era, as LA 2203.)

The pre-1955 system eventually reached the 22xx numeric range (or so) at its zenith. There were also "C-xxxx" roads, the purpose of which is unclear. All roads were seemingly numbered in the order that they were taken into the system, which led to anarchy, inconsistency, and disorder prevailing among the system of numbered routes. Major through routes were often divided up into several different route designations, and the routing of several primary marked routes (such as the old LA 1 and LA 30) came to make little sense from a traffic flow perspective.

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