As you know, the development and settlement of land is uneven. Some territians, most favorable in climatic conditions, relief, geographical position, etc.D., settled first. Territories that are not so attractive, are learned later.
The development of the Volga region began in the 7-10th centuries with the lower reaches of the Volga River (Khazar Kaganate). Around the same time, and until the 13th century, territories are populated at the confluence of the Volga and Kama rivers.
Starting from the 15th century (Astrakhan and Kazan Khanates), territories in the Volga delta are deposited, to its tributary of the sura, the tributary of the Sura – the Belaya River, to Samara Luka and the Upper Prikamye.
From the middle of the 16th century, the development of the right bank, the emergence of Samara and Saratov has been undergoing.
The second half of the 18th century – the settlement of the Volga region.
The sequence of settlement of territories affected the density of the population. In areas previously mastered, the population density is higher.