Short answers, pulled from the story.
The Bithynia region stretches across northwestern Asia Minor, touching the Sea of Marmara to the south and the Black Sea to the northeast. Its borders shift depending on which ancient geographer you ask.
Zipoites assumed the title of king basileus in 297 BC. His son Nicomedes I rebuilt ancient Astacus as Nicomedia in 264 BC.
After being restored by the Roman Senate he bequeathed his kingdom through will to the Roman Republic in 74 BC. This transfer marked the end of independent Bithynian rule and set the stage for provincial administration under Rome.
Emperor Trajan appointed Pliny the Younger governor of the combined provinces of Bithynia and Pontus around 109/110 AD or 111/112 AD. This arrangement provided historians with valuable information concerning Roman provincial administration at that time.
The Sangarius River divided Byzantine Bithynia into two separate provinces during the 7th century. Only the area west of the river retained the name Bithynia.
Bithynia became a border region to the Seljuk Empire in the 13th century before falling to Ottoman Turks between 1325 and 1333. The transition marked the end of Byzantine control over the territory.