Mirslavl was founded in pre-Mongol times as one of the strongholds protecting the neighboring cities of Yuryev-Polsky and Suzdal. Researchers still argue about the original location of the fortress on the Nerl. According to one version, it was located downstream of the current village of Mirslavl near the modern border of the Yuryev-Polsky district of the Vladimir region and the Gavrilovo-Posad district of the Ivanovo region. The ancient castle allegedly stood on the right bank of the Nerl. There is a legend that it used to be a stronghold of the Mirslavl princes - the descendants of Yuri Dolgorukov.
No ship could pass along the river without their permission. In order to more reliably guard the important waterway and to raise the level of the river, a dam was built at the castle, where there was only a narrow passage through which boats and barges were passed. After repeated Tatar raids, the old castle was destroyed, and only ruins remained. The historical name Mirslavl (it is believed that it came from the phrase "I glorify the world" - the fortress appeared after the end of one of the feuds between the Suzdal and Rostov princes as a guarantor of the concluded peace) was inherited by the village that arose nearby. Only in the 1920s, according to the well-known GOELRO plan, life began to boil again on the ruins of the Mirslavl castle. There, on the historical site, on the foundation of the old fortress, a hydroelectric power station was built - one of the first on the Nerl and in our region in general.