Originally it was 51.1 km long, running from Munich South station to Bichl and was built from 1891 to 1898 in sections by the Lokalbahn AG company (LAG).

In 1900, the LAG electrified the section from the Isartalbahnhof (the station for the Isar River Valley Railway in Munich) to Höllriegelskreuth for suburban services at 580 volts DC.

After the Second World War, Deutsche Bundesbahn converted the electrification to 15 kV AC (16 ⅔ Hz); this was completed in 1955 and extended to Wolfratshausen in 1960.

[3] On 24 January 1886, Siegfried Klopfer requested a license to build a metre gauge line from Munich via Wolfratshausen to Leoni on Lake Starnberg.

A letter of protest was written to the royal district office suggesting that the long distance from the station to the market place would take three quarters of an hour to walk.

[3] In 1888, Ernst Boehringer continued to refuse to relocate the Wolfratshausen station, which would require additional costs of up to 80,000 gold marks per kilometre.

[7] On 6 November 1889, the Lokalbahn Aktien-Gesellschaft und Cie. (Isartalbahn) was established for the construction and operation of the Isar Valley Railway.

This gave Wolfratshausen another chance to get a station in its valley if it ceded the land for the construction of the railway for free.

The concession for the construction and operation of the Isar Valley Railway was issued to the LAG by Prince Regent Luitpold on 21 April 1890.

The negotiations dragged on because the LAG wanted to build a tram line from Sendlinger Tor to the station of the Isar Valley Railway.

[12] Passenger services began on 1 June 1892 as the station building of the Isar Valley Railway was not ready until that time.

Freight operations started shortly after the opening of the line in 1892 and in 1893, the largest loads occurred because, after an infestation of the Forstenrieder Park by Black Arches caterpillars, the damaged wood had to be removed quickly.

The latter station opened up the possibility that the neighbouring municipality of Grünwald, which from 1910 had an interurban tram line of the Munich Tramway, could have its own railway connection.

As the use of electric railcars would be more economic, the LAG requested approval for the electrification of the line from Munich Isartalbahnhof to Höllriegelskreuth.

In 1933, the requirement to seek higher fares was abolished by the State Railway due to the poor financial condition of the LAG.

The German Post Office additionally reduced the number of postal bus route running parallel.

At the end of 1933, the Isar Valley Railway could operate eleven pairs of trains between Munich and Wolfratshausen again.

The munitions factory was built in 1939 and connected by a rail siding to the Isar Valley Railway in Wolfratshausen.

As the destruction of Munich increased, Deutsche Reichsbahn established a connection from the siding to the south, producing a triangular junction in Wolfratshausen, allowing freight trains to run via Bichl and Tutzing.

In order to transport freight from the munitions plant the Isar Valley Railway was restored to service provisionally, but due to the lack of spare parts only salt-impregnate sleepers could be used.

After the Second World War, traffic on the Isar Valley Railway was restored to normal operations only slowly.

In the 1950s, losses of an average of 2.8 million Deutsche Marks were incurred each year on the Isar Valley Railway.

[21] Since the rebuilding of the track was no longer worthwhile due to the low passenger numbers, Deutsche Bundesbahn decided in early 1958 to close the section from Beuerberg to Bichl.

The section was closed on 31 May 1959, at the start of the summer timetable, for passengers and freight traffic and it was dismantled in December of the same year.

In the early 1960s the city of Munich was planning the development of the Middle Ring, requiring the closure of the level crossing at Brudermühlstraße.

On 27 May 1972, the section from Wolfratshausen to Beuerberg was closed due to declining passenger numbers and also replaced by DB buses.

[3] In 1970, the platforms between Grosshesselohe Isartal station and Wolfratshausen were raised to a height of 76 centimetres in preparation for S-Bahn operations.

At the same time Deutsche Bundesbahn built a connecting curve with two tracks from Großhesselohe, which allowed the S 7 service to run at 20-minute intervals.

The remains of the branch line runs as a siding past the Isartalbahnhof and nowadays serves as a connection to the power station.

After crossing the Loisach over a 150-metre-long (490 ft) bridge, the line is reaches its current end point at Wolfratshausen station.