The history of Shlisselburg dates back to the deep Middle Ages. The city was founded in 1323 by the Moscow Prince Yury Danilovich, who was ruling in Novgorod at the time. Initially, it was a wooden fortress erected on the small Orekhovy Island at the source of the Neva River, which gave the settlement its historical Russian name — Oreshek. It was here, in the year of its foundation, that the famous Treaty of Nöteborg was signed, which for the first time officially established the border between the Novgorod Republic and the Kingdom of Sweden.
The development of the city and its fate were predetermined by its exceptional strategic position. Its location at the very source of the Neva from Lake Ladoga allowed the garrison to fully control the entry of ships into the river, effectively locking the waterway. Oreshek served as the main defensive outpost of the Novgorod land, protecting the northern borders from external expansion, and was also located on a busy trade route connecting the Baltic with the internal regions of Rus, ensuring a constant flow of goods and funds.
In the early period of its existence, the lifestyle in Oreshek was distinctly militarized. As early as 1352, after a fire, the wooden fortifications were replaced with stone walls and towers, making the fortress one of the most advanced fortification structures of its time in northwestern Rus. A settlement (posad) gradually formed around the citadel, and the economy of the early city relied not only on military salaries but also on the crafts necessary for servicing the army and navy, as well as on trade with passing merchant caravans.