[4][5] Archaeological finds also shows that Hungarians settled in the plains along the river after their arrival in the Carpathian Basin at the end of the 9th century.

[9][10] The Maros formed the northern border of Ajtony's realm, according to the Gesta Hungarorum, but the longer version of the Legend of Saint Gerard wrote that he controlled the lands as far as the Körös River.

[12] According to a scholarly theory, first proposed by historian György Györffy, Stephen I established Arad County after Ajtony's fall.

[13] At an assembly held in Arad in 1131, the wife of King Béla the Blind, Helena of Rascia, ordered the massacre of 68 Hungarian lords.

[2][7] The first known ispán, or head, of Arad County, Paul Csanád, was mentioned in a royal diploma, dated to 1214, but its authenticity is suspect.

[16] Members of the Csanád, Csák and Dorozsma clans received estates in Arad County in the early 13th century.

[16] Solymos Castle (in present-day Șoimoș in Lipova), the first fortress built by a nobleman in the county, was erected after the withdrawal of the Mongols.

[16] Ecclesiastic institutions, prelates and lay lords – including the bishop of Csanád, the Arad Chapter and the Garais, Lackfis and Telegdis – held most former royal estates in the first half of the 14th century.

[18] The earliest Romanian place name in the county – Caprewar (now Căprioara) – was recorded in a list of the estates of the Telegdis which was completed in 1337.