From 1912 it started an extensive cooperation with its main competitor, Kristiania Elektriske Sporvei (KES).
The first plans for horsecar operations in Oslo—then known as Christiania—took place in 1868, when Engineer Jens Theodor Pauldan Vogt and Architect Paul Due applied for a concession.
A new application was issued in 1873 with a common section with four branches, along Drammensveien, Gamlebyen, Oslo West Station (Vestbanen) and Grünerløkka.
[1] Vogt and Due's concession was transferred to a company, A/S Kristiania Sporveisselskab, which was incorporated on 26 August 1874.
[3] The company was permitted to use tracks on top of the roads, although the municipality retained the right at any time to require them to be dug down.
[1] Because of the location of the depot and the low traffic estimates along Drammensveien, KSS opted to instead build a branch to Homansbyen.
Regular traffic started on 6 October, as the second horsecar system in the Nordic Countries, after Copenhagen.
[1] Oslo was at the time a highly segregated community with little interaction between the higher and lower classes.
[5] At first there were no regular stops, the horsecar would simply lower its speed and allow people to jump on and off where they wished.
[6] Profits were made immediately, and in 1877 an additional seven cars were delivered,[7] allowing the headway to drop to five minutes.
[10] In conjunction with this a new depot was built at Olaf Ryes plass with place for fifty horses and a number of horsecars.
From 9 July 1880 all routes terminating at Stortorvet were merged, resulting in direct services from Homansbyen to Oslo and from Grünerløkka to Vestbanen.
They were so heavy they needed to be hauled by two horses and were designed with the intention of being used as trailers for the electric trams.
[15] To alleviate the situation, KSS's board approved plans in December 1897 for electrify their network.
As tracks for an electric tramway had to be designed to allow for return current, an all-new trackage would have to be laid.
There was a general understanding for the conversion in the public, although there were many protests against installing overhead lines in Karl Johans gate.
Forty-seven Class U units were delivered in 1899, with electrical equipment from Union and bodies built by Falkenried and Linke-Hofmann-Busch.
[22] That year there was a political debate regarding an expansion of the KSS' tramway towards St. Hanshaugen and Sagene, two areas which were being developed.
The decisive municipal council meeting was held on 14 April 1905, although the actual vote did not occur until 02:00 hours the following day, after a nine-hour debate.
[28] The Conservative majority voted in favor of selling KKS to KSS and extending the latter's concession to 1924.
[29] With the takeover KSS required not only three lines, but also a fleet of twenty Class S motorized trams and twelve trailers.
They were sold with a quantity discount and were commonly used in Oslo as a conventional coin worth 15 øre.
KES and the labor union could not reach an agreement for wage increases and the company was hit by a strike from 11 January to 22 March 1920.
The committees majority proposed a merger and that KSS received a prolonged concession, while the minority recommended that the tramways be bought by the city.
[42] The issue was considered by the council's executive board, which supported the joint public–private proposal with eleven against nine votes.
[42] The issue was voted on in the municipal council in December, with 43 against 41 councillors supporting the joint model.
After the closing of the horsecar network, thirty-eight units were converted to trailers for electric trams.
[37] The first class was built by John Stephenson Company and consisted of twenty-nine units delivered in 1875 and 1877.
Measuring 6.6 meters (22 ft) in length, they were sufficiently heavy they needed to be hauled by two horses.
[49] KSS took delivery of thirty-seven Class SS motorized trams and twenty-two trailers between 1912 and 1914.