Pergamon
Pergamon lies on the north edge of the Caicus plain in the historic region of Mysia in the northwest of Turkey. The Caicus river breaks through the surrounding mountains and hills at this point and flows in a wide arc to the southwest. At the foot of the mountain range to the north, between the rivers Selinus and Cetius, there is the massif of Pergamon which rises 335 metres above sea level. The site is only 26 km from the sea, but the Caicus plain is not open to the sea, since the way is blocked by the Karadağ massif. As a result, the area has a strongly inland character. In Hellenistic times, the town of Elaia at the mouth of the Caicus served as the port of Pergamon. The climate is Mediterranean with a dry period from May to August, as is common along the west coast of Asia Minor.
Eumenes I
Although nominally under Seleucid control, Pergamon under Philetaerus enjoyed considerable autonomy. However, upon his succession, Eumenes, perhaps with the encouragement of Ptolemy II, who was at war with the Seleucids, revolted, defeating the Seleucid king Antiochus I near the Lydian capital of Sardis in 261 BC. He was thus able to free Pergamon, and greatly increase the territories under his control. In his new possessions, he established garrison posts in the north at the foot of Mount Ida called Philetaireia after his adoptive father, and in the east, northeast of Thyatira near the sources of the river Lycus, called Attaleia after his grandfather, and he extended his control south of the river Caïcus to the Gulf of Cyme as well. Demonstrating his independence, he began to strike coins with the portrait of Philetaerus, while his predecessor had still depicted Seleucus I Nicator.