Tokaido (or Umitsu-Michi) can mean:
One of the Goki-Shichido, an ancient administrative area, on the Pacific Ocean side of central Honshu.
One of two highways that traverse the above-mentioned Tokaido region.
A highway that was built during the Ritsuryo period.
A highway that was built during the Edo period. This highway was one of the Go-kaido (the collective name given to the five principal routes used during the Edo period).
As an administrative division, Tokaido referred to a region of Central Honshu extending east of Kinai and along the Taiheiyo. This corresponds to the regions stretching from present-day Mie Prefecture to Ibaraki Prefecture along the Pacific coast.
Iga-no-kuni (western Mie Prefecture)
Ise-no-kuni (central Mie Prefecture)
Shima-no-kuni (eastern Mie Prefecture and the vicinity of the Irako Cape, in Aichi Prefecture)
Owari-no-kuni (western Aichi Prefecture)
Mikawa-no-kuni (central and eastern Aichi Prefecture)
Toto-umi-no-kuni (mainly western Shizuoka Prefecture)
Suruga-no-kuni (mainly Central ShizuokaPrefecture and the vicinity of Mt. Fuji)
Izu-no-kuni (Izu Peninsula and the Izu island chain)
Kai-no-kuni (Yamanashi Prefecture)
Sagami-no-kuni (Kanagawa Prefecture)
Musashi-no-kuni (Tokyo Prefecture and part of Saitama and Kanagawa Prefectures,
initially belonging to Tozando).
Awa-no-kuni (southern Chiba Prefecture)
Kazusa-no-kuni (central Chiba Prefecture)
Shimo-usa-no-kuni (east of the Sumida River in Tokyo Prefecture, northern Chiba Prefecture and part of Ibaraki Prefecture)
Hitachi-no-kuni (Ibaraki Prefecture)
The Ritsuryo Period
During the Ritsuryo period the Tokaido was a road linking the Kokufu and Tokaido regions. The Tokaido, one of the Shichido, is in the middle grade among the Goki-Shichido. During the Ritsuryo period the Tokaido was developed to be wider and straighter than that of the middle ages and the Edo period.
A question remains as to what the exact route would have been because the road was no longer used and had disappeared over the middle ages, but its route is thought to be nearly the same as the modern Tokaido except for the following areas:
The area from Numazu to Sekimoto via Gotenba and Ashigara-toge
In those days the Tokaido was the main road in "Tokaido." After the Ashikagaji was closed in about 800 due to an eruption of Mt. Fuji, the "Hakone-ji" was developed and called "Tokaido Yagurazawa Okan." However, because the route of the Hakone-ji had steep slopes, the Ashigara-ji was repaired and reopened, and it continued as a major highway until the middle ages.
East of Sagami-no-kuni Kokufu
After crossing the sea, the Tokaido ran north along the Boso Peninsula, went through Hitachi-no-kuni and the Kikuta-no-seki checkpoint into Mutsu-no-kuni, and merged with the Tozando in what is now Miyagi Prefecture.
In Sagami-no-kuni it took the route of the present Yagurazawa-okan (National Highway 246) until the point of crossing the Tama-gawa River. In some sections of the old route of the Yagurazawa-okan, the roadway of the Tokaido in the Ritsuryo period has been used.
In ancient times a border area between Musashi-no-kuni and Shimo-usa-no-kuni, called the Nakagawa Lowlands, had not become solid land and was therefore unsuitable as a travel route, but Musashi-no-kuni belonged to Tozando under the traditional influence of the powerful families of its northern neighbor Ueno-no-kuni, and had a close relationship with them (see the article on Musashi-no-kuni-nomiyatuko-no-ran). Accordingly, the initial Tokaido crossed water from the Miura Peninsula of Sagami-no-kuni to the Boso Peninsula of Kazusa-no-kuni (Awa-no-kuni became independent in 718). This is because, apart from Awa-no-kuni, present-day Chiba Prefecture (the tip of the Boso Peninsula), Kazusa-no-kuni (the central Boso Peninsula), having the kanji meaning "upper," was in fact below Shimousa-no-kuni (the upper part of the peninsula), having a kanji meaning "lower," which may feel confusing by comparison to the modern concept of "upper and lower."
Later, on October 27, 771 (on the old Japanese calendar), Musashi-no-kuni was transferred to Tokaido in consideration of an insecure water route and the importance of efficient transportation in sending an expedition to Ezo (according to Shoku-Nihongi). It is believed that the name "Tokaido" includes the meaning "Umi-no-michi" (literally, "sea road") rather than "Yama-no-michi" (literally, "mountain road," which is the meaning that the name "Tozando" includes) because, in addition to the route from Sagami to Kazusa mentioned above, it also provides a route across the sea at Ise Bay from Mikawa-no-kuni to Ise-no-kuni. The water route was described in Engi-shiki.
The Tokaido, after reaching its terminal region of Hitachi-no-kuni, was extended further north to Mutsu-no-kuni via the Kikuta-no-seki checkpoint. It continued along the coastal area of the present-day Fukushima Prefecture (along Hama-dori street) and merged with the Tosando in Iwanuma City, Miyagi Prefecture. The Tokaido in Mutsu is a secondary route, because Mutsu belonged to Tozando. In regions north of Mutsu, roads with the Tokaido name are found here and there. If they are legacies of ancient times, it is likely that the Tokaido existed as a branch line in regions farther north. The roads described in historical papers as sea routes (in contrast to mountain routes) are believed to have been developed as branch lines extending from Kokufu of Tagajo toward Oshika-gun/Monou-gun. Also, Azuma-kaido Street in present-day Sendai may have a story that goes back to ancient times.
The Middle Ages
In those days Umimichi referred to the Tokaido, as described in a book entitled "Kaidoki."
The Edo Period
In the beginning of the Edo period, when the administrative capital was transferred to Edo (Tokyo), the Tokaido was regarded as one of the five major highways and thus became the most important route linking Kyoto and Edo. It extended from Nihonbashi (Chuo Ward, Tokyo Prefecture) (Edo) to Sanjo-ohashi (Kyoto City). There were 53 yadoeki (see "Tokaido Gojusan Tsugi"). Military activity was the original purpose of the improvement of the Tokaido. Checkpoints were established along the way in Hakone Town and Arai Town.
Some may regard the Kyo-kaido (with four checkpoints), which extended from Kyoto to Osaka, as part of the Tokaido. On the way, in the direction from Edo to Osaka, the Otsu-kaido branched off at Oiwake Station (Shiga Prefecture) to enter Fushimi Ward instead of entering Kyoto at Otsu-juku.
Work Pieces Featuring Tokaido
Tokaidochu Hizakurige, by Ikku Juppensha
The Meiji Period and Onward
The Meiji government began to assign road numbers as the names of national arterial highways, and thereby it abolished Ryoseikoku as a regional division system. The proper function and location of the highway were taken over by the present national highways 15 and 1. Although the current Tokaido takes a different route in some sections, its function of linking eastern Japan with western Japan (or the Kanto region with the Kansai region) has been the same since the Ritsuryo period, which means the route of the Tokaido is still indispensable for Japan today.
When people say "Tokaido" today, they refer to its route in the Edo era and the areas that belonged to the region of Tokaido in those days. Therefore, the east end of Tokaido was Kitaibaraki City in the Ritsuryo era and the special word (Edo) in the Edo era and later.
Tokaido as a Railway
The Tokaido Main Line and Tokaido Shinkansen, which both include "Tokaido" in their names, roughly follow the Tokaido between Tokyo and Atsuta and between Kusatsu and Kyoto, but between these two sections of the route, they follow the Nakasen-do (between Kano-juku and Kusatsu-juku) and then the Mino-ji Highway (between Miya-juku and Tarui-juku). Today some people misunderstand and even show others that the route taken by these two railways is that of the "Tokaido" of the Edo period. As explained below, the true Tokaido as an historical highway roughly follows the route of Nagoya - Kameyama - Kusatsu, which is somewhat closer to the route taken by the present Kansai Main Line and the Kusatsu Line.
Behind this lies a construction plan of the early Meiji period, and there were divided opinions over which route--Tokaido or Nakasen-do Street--would be preferable for construction. Initially the government accepted the route along Nakasen-do Street and started service in some sections, but later it realized that the route along the Tokaido was better, considering the earlier plan's higher estimated costs and longer construction period, as well as the restricted transportation in mountainous areas (particularly those across the Usui-toge), so ultimately the route was shifted east of Kano (Gifu Prefecture) to the route along the Tokaido.
When it was decided that the plan would be changed, the line of Kobe Station (Hyogo Prefecture) - Osaka Station - Kyoto-Station - Otsu Station and the line of Nagahama Station - Gifu Station - Nagoya Station -Taketoyo Station had already been opened. They also thought it would be better to construct the trunk line connecting the ancient capitals and new capitals as early as possible by making use of already-built lines and ferry service on Lake Biwa (Otsu - Nagahama), thereby establishing the present route.
As the result, Japan's first railway line from Shinbashi to Yokohama was incorporated into this east-west trunk line. The construction started in the section from Yokohama Station to Obu Station via Shizuoka Station and in the section from Sekigahara Station to Otsu Station via Maibara Station in the mid-1880s, and in July 1889 the entire line was opened with the completion of the prototype for the current Tokaido Main Line.
In the middle of the Meiji, for the area from Atsuta to Kusatsu via Yokkaichi-juku, which diverges from the east-west truck line above, Kansai Railway Company set up rails for the purpose of promoting the area's development, and subsequently it became part of the current Kansai Main Line (from Tsuge Station to Nagoya).
In the construction of the Shinkansen, although the initial plan was to build a straight tunnel under the Suzuka Sanmyaku mountain range, the current route of the Tokaido Main Line was finally accepted in consideration of the costly and time-consuming task of making such a tunnel and the role of Maibara Station as a junction to the Hokuriku Main line (formerly Hokuriku-do).
Please refer to the "Nakasen-do Street" and "Railways and Politics" sections for additional details.