With no wars on the island, and no interaction with anyone, infrastructure in Japan was developed during this time.
Economic Growth
Cities like Edo would grow in size, due to the merchants coming in and the daimyo building their castles.
The merchants, though being the lowest class in the Tokugawa social structure, would become some of the richest people in Japan.
Education
There was a new emphasis on education and literacy in this era, causing a growth in published works as well.
Terakoya ("temple schools") were created and provided education to commoners.
Japan would become one of the most literate countries in the world.
Infrastructure
The shogun organized trade within Japan, creating standardized measurements and a currency that everyone could use.
Transportation was developed, roads were made between cities, and rest stops were created on long roads.