Short answers, pulled from the story.
The year 305 CE marks the completion of Diocletian's Palace, yet Split existed as a Greek colony named Aspálathos centuries before that stone was laid. Archaeologists estimate this settlement arose during the third or second century BCE on the coast inhabited by the Dalmatae people.
The polis of Issa located on modern-day Vis founded this early trading post to serve as a commercial hub for exchange with surrounding Illyrian tribes particularly the Delmatae. No exact founding date survives in historical records but trade routes connected these coastal communities long before Roman emperors arrived.
Salona fell to Pannonian Avar forces in 639 destroying the ancient capital of Roman Dalmatia. Surviving Romans fled across the water to nearby islands before returning under Severus the Great in 650 to take possession of the three-hundred-year-old Palace of Diocletian.
Italy annexed Split on the 18th of May 1941 when Treaties of Rome were signed placing it in the province of Spalato. The Italian Governatorate hosted three hundred ninety thousand inhabitants including two hundred eighty thousand Croats and ninety thousand Serbs.
Brodosplit employed around two thousand three hundred people and had built over three hundred fifty vessels including tankers container ships frigates submarines and passenger ships. The shipbuilding industry became particularly successful making Yugoslavia one of the world's top nations in that field.