Musashi bordered on Kai, Kōzuke, Sagami, Shimōsa, and Shimotsuke Provinces.
Musashi was the largest province in the Kanto region.
Edo Castle was the headquarters of Tokugawa Ieyasu before the Battle of Sekigahara and became the dominant city of Japan during the Edo period, being renamed Tokyo during the Meiji Restoration.
Provinces as part of the system of addresses were not abolished but, on the contrary, augmented.
Provinces are nonetheless today considered obsolete, although their names are still widely used in names of natural features, company names, and brands.
Some of the province names are used to indicate distinct parts of the current prefectures alog with their cultural and geographical characteristics.