The "Main Line", in popular usage, refers to the more rural section east of Chiba.

For more details of services west of Chiba, see the relevant articles for the Local and Rapid Lines.

Shiosai, also a Limited Express service, which operates from Tokyo Station to Chōshi, also uses this line.

Tokyo - Shin-Nihombashi - Bakurochō [ Ochanomizu - Akihabara - Asakusabashi - Ryōgoku - Kinshichō ] Kameido - Hirai - Shin-Koiwa - Koiwa - Ichikawa - Moto-Yawata - Shimōsa-Nakayama - Nishi-Funabashi - Funabashi - Higashi-Funabashi - Tsudanuma - Makuharihongō - Makuhari - Shin-Kemigawa - Inage - Nishi-Chiba - Chiba For the connections of the line, see the route diagram.

It opened the first service sections, between Ichikawa and Sakura on July 20, 1894, and extended to Tokyo City.

The predecessor of the Japanese National Railways (JNR) planned to connect with other lines inside Tokyo.

In 1932, a new passenger line was opened from Ochanomizu to Ryōgoku (with new platform besides the original terminal facility), and a frequent service of EMUs[clarification needed] commenced.

On March 10, 1945, the Bombing of Tokyo caused casualties estimated at 70,000–100,000, and destroyed stations of the line.

To the east of Chiba, electrification reached Chōshi in 1974, and Limited Express Shiosai has been operated from the underground Tokyo Station since 1975.

Freight services from Chōshi ceased in 1986, just before the privatization of JNR, and regular passenger trains stopped using the Ryōgoku terminal platforms in 1988.