Philetaerus who had served under Lysimachus was the ruler of Pergamon, Lysimachus' treasury, at that time, exercised some autonomy under the Seleucids who seized Lysimachus' lands, ruling from 282–263 BC. The subsequent dynasty was named Attalid, in honour of Philetaerus'father Attalis. On his death he was succeeded by his nephew Eumenes I (263–241 BC), who revolted against Seleucid rule and defeated Antiochus near Sardis in 262 BC, guaranteeing Pergamon's independence. Eumenes enlarged Pergamon to include parts of Mysia and Aeolis, and held tightly onto the ports of Elaia and Pitane. Eumenes was succeeded by his nephew Attalus I (241–197 BC) who was the first dynast of Pergamon to assume the title of 'king'. He succeeded in defeating the plundering Galatian Gauls, who had become an increasing problem in Anatolia, in 230 BC. Athena Nikephorus's (The Victory Bearer) temple was decorated with Epigonus' famous statues of the defeated Galatians. Attalus protected the Greek cities of Anatolia but harassed the Macedonians on the mainland, allying himself with Rome during the Macedonian Wars. A series of wars against Antiochus Hierax gave Pergamon control over much of Seleucid territory north of the Taurus Mountains, only to lose it under Antiochus III. The dealings with Attalus proved to be the last time the Seleucids had any meaningful success in Anatolia as the Roman Empire lay on the horizon. After that victory, Seleucus's heirs would never again expand their empire. Attalus also had to fight off neighbouring Bithynia, under King Prusias (228 – 182 BC).
