Juan Carlos I of Spain was born on January 5, 1938, in Rome, Italy. He became the King of Spain in 1975 after the death of Francisco Franco, the country's dictator. His reign marked the transition of Spain from a dictatorship to a parliamentary democracy, and he played a crucial role in establishing a constitutional monarchy. During his time as king, Juan Carlos I was known for his efforts to modernize Spain and promote democratic values. He abdicated the throne in June 2014, passing the crown to his son, Felipe VI, after nearly 39 years of reign.