TheLudwig South–North Railway (Ludwig-Süd-Nord-Bahn), built between 1843 and 1854, was the first railway line to be constructed byRoyal Bavarian State Railways. It was named after the king,Ludwig I, whose infrastructure priorities had earlier been focused less on railway development than onhisMain-Danube canal project.

The railway ran fromLindau onLake Constance viaKempten,Augsburg,Nuremberg andBamberg toHof where it linked up with theSaxon-Bavarian Railway Company.

Following the successful experiment involving the construction of a railway connectingMunich toAugsburg, which had opened on 4 October 1840, committees sprang up in many parts ofBavaria to plan private railways. The government determined that the building of further railways should become a state responsibility, however. On 14 January 1841 Bavaria concluded withSaxony andSaxe-Altenburg an agreement to build a railway connectingLeipzig withNuremberg, which would cross into Bavaria atHof. The parties committed to have the railway ready for operation within six years.

The Bavarian government decided to extend the railway pastAugsburg (already connected by rail toMunich, the capital city) through theAllgäu as far asLake Constance. The necessary legislation was passed in Munich on 25 August 1843. With a budgeted cost of 51.5 millionGuilders, it was planned that the entire length would be ready within ten years. The section between Augsburg and Hof would account for 33 million guilders. Space for two tracks would be prepared, but initially only a single track would be laid. Responsibility for the construction would be given to chief engineer, August Pauli and, initially, the French-born railroad pioneerPaul Camille von Denis, though Denis had been taken off the project in 1842 in order to take over the construction of a line connectingLudwigshafen (at the time also ruled by Bavaria) withSaarbrücken (subsequently named thePalatine Ludwig Railway (Pfälzische Ludwigsbahn).

The privately owned Saxony-Bavaria Railway Company, in which the governments ofSaxony andSaxe-Altenburg held a minority stake, started work on the Saxon end of the railway line in 1841.

In Bavaria, following the establishment in 1841 of theNuremberg-based Royal Railway Building Commission, work began on ground preparation in 1842, but due to topographical challenges of the kind familiar to later generations of railway builders, serious construction began only in 1843. Sometimes-conflicting objectives included the avoidance of over-steep sections while nonetheless connecting as many towns and cities as possible with the railway. Nevertheless, on the slopes of theFichtel Mountains betweenNeuenmarkt andWirsberg, the route incorporates a stretch with an average gradient of 23‰.

The first stretch of line, between Nuremberg andBamberg, was opened to passengers in October 1844. The full 203 kilometers of the northern section were opened in five successive stages, the fifth, betweenHof and the frontier with Saxony, opening in November 1848. A celebration of the opening of the first sections of the line took place at Nuremberg on 25 August 1848, which was the king's birthday, by when the line already extended north as far as Neuenmarkt.

Although the Bavarian part of the project had overshot the agreed six-year time line, it was still ready ahead of theSaxon part, full opening of which was delayed by topographical challenges until 1851.

To the north of Nuremberg, atErlangen where the line ran parallel to theLudwigs canal (the Rhine-Main-Danube canal of that time), the railway incorporated the 306-meter-long Burgberg tunnel, Bavaria's oldest railway tunnel.

From 1852 there was a connection at Bamberg with the newLudwig's Western Railway towardsWürzburg,Aschaffenburg and, by 1854, theHessean frontier atKahl.

After the unification of Germany in 1870, Hof ceased to be a frontier town and the line became a significant component of the national rail network. Between 1862 and 1892, the opportunity was taken to install a second track, for which space had already been allowed at the time of the original construction: by 1939 electrification had been completed from Nuremberg as far as Bamberg. In 1945, however, following theSecond World War, Germany was partitioned, withBavaria in theUS occupation zone (which subsequently became part ofWest Germany andSaxony in theSoviet occupation zone (which subsequently becameEast Germany). The line lost importance. In the 1960s, over a ten-kilometer section betweenMarktschorgast andStammbach, the second track was removed since the level of traffic had become too low to justify maintenance of a parallel track over this mountain section.

The railway's decline was reversed with theunification of the two post-war German states: since 1990 the line has recovered much of its former importance. The route of the northern section of the Ludwig South–north railway has changed little since 1848.

Work had also started on the central section in 1843, and the first section, betweenOberhausen and Nordheim (now a district ofDonauwörth) was opened in November 1844. By the end of 1849 the entire middle section had been completed. Thecapital was linked in to the national rail network on 1 June 1846 when theMunich–Augsburg railway found itself nationalised in return for a shareholder compensation payment of 4.4 MillionGuilders.

The section ran relatively indirectly between Nurmenburg and Augsburg, partly for topographical reason and partly because it was hoped this would facilitate an interchange atNördlingen with theRoyal Württemberg State Railways, an aspiration that would be fulfilled from the Württemberg side of the frontier only in 1861.

AtDonauwörth the line included Bavaria's second oldest tunnel, although the 125 meter long tunnel would become redundant for its original purpose after 1870 when the route roundDonauwörth was changed. Today the south-eastern end of the tunnel, which lies directly beyond the site of the former station, has been converted for warehousing and residential uses.

Before the southern portion of the railway had been completed, work had already begun inAugsburg on theMaximilian Railway(Bayerischen Maximiliansbahn) which would run westwards towardsNeu-Ulm and the frontier withWürttemberg. The landscape to the west of Augsburg was less challenging than the route to the south, and the line towardsUlm could already be opened as far asDinkelscherben on 26 September 1853.

By 1852 the Ludwig South–north railway extended as far south aKempten where a large timber bridge,the King Louis Bridge, built for two tracks carried it over the RiverIller. The bridge would be replaced by a concrete structure, but not before 1906. Just 7 kilometers further along the line towardsImmenstadt, atWaltenhofen, came another large timber bridge. This 53 meter long structure would be replaced by a steel bridge in 1900. Between Immenstadt and Lindau the line follows two difficult mountain passes in order to avoidWürttemberg, at that time still a foreign state. The final 1.8 kilometers, opened early in 1854, ran along the wall protecting the town fromLake Constance.

The entire route having been completed on 1 March 1854, 566 kilometers of line with space for two tracks had been completed in less than eleven years: this represented a remarkable achievement in view of the resources then available.

• 1843 establishments in Bavaria
• Railway lines opened in 1843
• Railway lines in Bavaria
• Defunct railway companies of Germany
• Ludwig I of Bavaria

• CS1 German-language sources (de)
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