from Greek: peran (Iordanou) ["beyond Jordan"]

District on the east side of the Jordan river whose northern border was south of Pella in the Decapolis & whose southern border was guarded by the frontier fortress of Machaerus. In antiquity the region had belonged to Israel's bitter rivals, the kingdoms of Ammon & Moab, which were conquered by David (10th c. BCE). After Solomon, during the time of the divided monarchy (9th-8th c. BCE), it was known as Gilead & was the homeland of Elijah. For about 600 years the region was lost to Israelite control, but was reconquered by Johanan Hyrcanus (ca. 120 BCE) & its inhabitants forcibly converted to Judaism. Augustus assigned Perea to Herod, who willed it to Antipas. After Herod's death Perea became the center of a brief  but bloody revolt led by a former royal slave named Simon.

This was the area of the activity of Johanan the Baptizer [according to John 1], including his imprisonment & execution at Machaerus [according to Josephus]. According to the synoptic gospels, Jesus took the Jordan valley road through Perea that ran from the southern end of the Sea of Galilee to the ford at Jericho on his way to Jerusalem.

References: Josephus, Antiquities 13.50; 15.294; 17.188, 276, 318; 18.240; 20.2-3. 
                   _____, War 1.586; 2.57-59, 94-95, 168, 566-568.
                   Mark 3:8 // Matt 4:25 
                   Mark 10:1 // Matt 19:1
                   John 1:28, 3:26, 10:40

For further recent information about archaeological & historical evidence, see:

• Buttrick, G. A., ed. Interpreter's Dictionary of the Bible. vol. 3 (NY/Nashville: Abingdon Press, 1962) pp. 728-729.

Other resources on line:

• Perea (Holy Land) - brief entry in Wikipedia's web includes map.