The Saint Margaret Mountain is very old. The first document that mentions it is the so-called "Trzemeszno forgery" (created around 1233 in the monastery of the Lateran Canons in Trzemeszno), dated 28 April 1145. According to it, in that year, in the presence of the papal legate Cardinal Humbald, one of the sons of Bolesław Krzywousty (probably Mieszko III the Old) gave the "village on the Mountain near Łęczyca" into the possession of the monastery of the Canons Regular of the Lateran in Trzemeszno. The document also mentions the Chapel of Mary located in this village; so in 1145 both the village and the chapel already existed, but the date of the village's foundation is unknown. The Geographical Dictionary of the Kingdom of Poland (1881 edition) gives the year 1040, but this is not substantiated in any way. The etymological dictionary of towns and communes of the Polish People's Republic already refers to the "Trzemeszno forgery" and gives the year of foundation as 1145. Ultimately, this date was recognized as the year of foundation of the village, whose owners were the Canons Regular of Trzemeszno.