The line was electrified by June 1919, and the southern terminus extended to Shuzenji Station on August 1, 1924.

In May 1933, regularly scheduled weekend services to Tokyo Station began operation but were later suspended during World War II.

A rail yard and train factory was completed at Daiba Station on June 10, 1937.

In 1949, the Japan National Railways began semi-express and limited-express train operations from Tokyo.

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