“The Showa reign was a year and five days old when, late in 1927, the first Tokyo subway line began service. It was the first in the land, and in Asia. The route was a short one, less than a mile and a half long, between Ueno and Asakusa. Four companies had franchises to dig; only one started digging. The same company extended the line to Shimbashi in 1934.
“The entrepreneur who owned all the land around Shibuya and brought the private commuter into it saw his opportunity. Shimbashi must not remain the terminus. So he started digging from Shibuya, and his line was opened to Shimbashi in 1939. There were [now] two Shimbashi stations, without free transfer between them.
“The two companies were brought together, and the stations united, in 1941, under a public corporation capitalized by the Imperial Government Railways and Tokyo prefecture.
“The two halves of the Ginza line, as it is now called, show a certain difference in spirit. The northern half, from Shimbashi to Asakusa, was dug by a company specializing in transportation and interested in pleasing its customers. Some of the stations are rather charming, in Art Deco and traditional styles … The stations south and west of Shimbashi are uniformly drab and boxlike, the product of an entrepreneur whose chief interest was getting hordes of people as rapidly as possible into the Toyoko department store [today’s Tokyu department store at Shibuya], on the third floor of which it ends. So we might say that the Ginza line symbolizes transition. The northern half belongs to the past, the southern half to the emerging future.”
– Tokyo Rising: The City Since the Great Earthquake, Edward Seidensticker, 1990
From the wiki: “The Ginza Line was conceived by a businessman named Noritsugu Hayakawa, who visited London in 1914, saw the London Underground and concluded that Tokyo needed its own underground railway. He founded the Tokyo Underground Railway (Tōkyō Chika Tetsudō) in 1920, and began construction in 1925.
“The portion between Ueno and Asakusa was completed on December 30, 1927 and publicized as ‘the first underground railway in the Orient’. Upon its opening, the line was so popular that passengers often had to wait more than two hours to ride a train for a five-minute trip.
“On January 1, 1930, the subway was extended by 1.7 km to a temporary station at Manseibashi which was abandoned in November, 1931 when the subway reached Kanda, 500 meters further south down the line. The Great Depression slowed down construction, but the line finally reached its originally planned terminus of Shinbashi on June 21, 1934.
“In 1938, the Tōkyō Rapid Railway (Tōkyō Kōsoku Tetsudō), another private concern tied to the predecessor of today’s Tokyu Corporation, Toyoko K.K., began a subway service between Shibuya and Toranomon. It was later extended to Shinbashi in 1939, at which time the two lines began through-service interoperation. The two were formally merged into the Teito Rapid Transit Authority (‘Eidan Subway’ or ‘TRTA’) in July 1941.
“The ‘Ginza Line’ name was formally applied in 1953 to distinguish the line from the then-new Marunouchi Line.
“According to a June 2009 Tokyo Metropolitan Bureau of Transportation survey, the Ginza Line is the seventh most crowded subway line in Tokyo, running at 168% capacity between Akasaka-Mitsuke and Tameike-Sannō stations.”