Please answer a question about the following article about Hellenistic period:

The Kingdom of Pontus was a Hellenistic kingdom on the southern coast of the Black Sea. It was founded by Mithridates I in 291 BC and lasted until its conquest by the Roman Republic in 63 BC. Despite being ruled by a dynasty which was a descendant of the Persian Achaemenid Empire it became hellenized due to the influence of the Greek cities on the Black Sea and its neighboring kingdoms. Pontic culture was a mix of Greek and Iranian elements, the most hellenized parts of the kingdom were on the coast, populated by Greek colonies such as Trapezus and Sinope, which became the capital of the kingdom. Epigraphic evidence also shows extensive Hellenistic influence in the interior. During the reign of Mithridates II, Pontus was allied with the Seleucids through dynastic marriages. By the time of Mithridates VI Eupator, Greek was the official language of the kingdom though Anatolian languages continued to be spoken.

When was the Kingdom of Pontus founded?
291 BC