The east of Iran has been neglected in archeology studies for the past decades and a century, and despite the very few studies that have been done on its findings, it shows the importance of this part of cultural Iran in territorial archeology studies. The cultural domain of eastern Iran, which corresponds to the southern parts of Greater Khorasan and areas of northern Sistan, has been the site of important historical events. South Khorasan has experienced many ups and downs throughout history and was known as a part of the Aryeh state in the historical era and as Qohestan in the Islamic era. The current geographical and political framework of the region consists of desert areas in the southern and western half and parts of the east, and the northern and central parts are mostly mountains and intermountain plains. South Khorasan in the historical period, due to being on the communication path of the eastern states of the empire and being located between two important geographical and political areas such as Zaranke/Sistan and Khorasan/Parth, played an important role in the political developments of this era, and the study of archaeological data and evidence The remnants of this era confirm this importance. The natural and geographical texture of this region and its location in the middle of the eastern states of Iranshahr have made this area to be considered as a link between the east and the imperial center in the historical period and as the gate of Khorasan and the grain storehouse of Iran in the Islamic period. The research is written in a descriptive-analytical method based on field and library sources. The purpose of the research is to study and examine the findings and archaeological evidence obtained from the historical period (Iron Age III - Sassanid) in the political area of South Khorasan and it is trying to answer these questions. 1- What is the most distribution of sites in the Iron Age in South Khorasan region? 2- South Khorasan region had cultural connections with which regions?