How did Vatican City become an independent state?

Vatican City became an independent state through the Lateran Treaty, signed in 1929 between the papacy and the Italian government.12

This agreement resolved the "Roman question," a long-standing dispute that began in 1870 when the Kingdom of Italy annexed the Papal States and made Rome its capital. Following this annexation, the popes refused to recognize the new Italian state and remained within the Vatican grounds as self-described "prisoners," a situation that persisted for nearly 60 years.134

The 1929 treaty formally ended this impasse by establishing Vatican City as a sovereign, independent nation-state. Under the terms of the treaty, the papacy recognized the state of Italy, and in return, Italy recognized papal sovereignty over the Vatican territory, ensuring the pope could exercise his universal authority independently.24