Analysis of information sources in references of the Wikipedia article "Library of Celsus" in Simple English language version.
Nevertheless, in 92 the same office went to a Greek, Ti. Julius Celsus Polemaeanus, who belonged to a family of priests of Rome hailing from Sardis; entering the Senate under Vespasian, he was subsequently to be appointed proconsul of Asia under Trajan, possibly in 105/6.
Ti. Julius Celsus Polemaeanus (PIR2 J 260) was a romanized Greek of Ephesus or Sardes who became the first eastern consul.
... and son of Julius Celsus Polemaeanus, proconsul of Asia, who founds the Celsian library from his own wealth ...
It was erected in Ephesus, in Asia Minor, in territory that was traditionally Greek to the core. That is why Celsus' library in Ephesus represents very important element in tracing the development of Roman libraries.