The Hanzōmon Line was first planned in 1968, along with the
Chiyoda Line and
Yūrakuchō Line, as a reliever line for the heavily congested
Ginza Line. Its initial routing was from
Futako-Tamagawa Station on the
Tōkyū Den-en-toshi Line to a new station in the Fukagawa district of
Kōtō. In 1985, a second draft plan from the Ministry of Transportation moved the Hanzōmon Line's final terminus to
Matsudo. During the planning stage, it was known as
Line 11. Construction began in 1972 and the majority of the line was expected to open in 1975. However, the
Teito Rapid Transit Authority did not have enough funds to build the line, which delayed its construction. On August 1, 1978, the first section of the Hanzōmon Line finally opened from Shibuya to Aoyama-itchōme, including through services with the Den-en-toshi Line. It was then extended to Nagatachō Station in September 1979. The line was initially operated mainly using Tokyu rolling stock, as the first TRTA 8000 series train did not enter service until 1981. However, the next extension posed political problems, as the original plan had the line run directly under the
Imperial Palace to
Ōtemachi Station. TRTA decided to divert the route around the north side of the Imperial Palace, which required the construction of three new stations. An
eminent domain battle erupted with landowners along the proposed route, which delayed the completion of the next stage of the line.
Hanzōmon Station opened in December 1982, and the full extension around the Imperial Palace, terminating at Mitsukoshi-mae, was not completed until January 1989. The line was then extended to Suitengu-mae in November 1990 and finally Oshiage in March 2003, the latter also enabling through service with the Tobu Skytree Line. The line, station facilities, rolling stock, and related assets were inherited by
Tokyo Metro after the privatization of the Teito Rapid Transit Authority (TRTA) in 2004. The
Ministry of Transportation recommended in 2000 that the line be extended to its intended terminus in Matsudo by 2015. However, Tokyo Metro stated in its
initial public offering that its construction operations would cease once the
Fukutoshin Line is completed, which cast some doubt as to whether the Matsudo extension will actually be built. ==Stations==