During the 19th century, Batumi was a battlefield of Russian and Turkish interests and finally, after the Russo-Turkish War of 1877-78, the defeat of the Turks brought Batumi under the control of the Russian Empire (together with a significant part of south-west Georgia). After the Preliminary Treaty of San Stefano, signed between the Russian and Ottoman Empires and the following Treaty of Berlin, Batumi was declared a free port (porto franco) and maintained this status until 1886.
By the end of 1870s, the construction of the sea port was finished and the expansion of Batumi began. The Batumi-Tbilisi-Baku railway was completed in 1900, just in time for the completion of the Baku-Batumi oil pipeline: there was a huge oil production centre in Batumi. Around this time, in 1888, Batumi was officially granted city status and the first mayor of Batumi was elected. Moreover, Batumi became the main Russian oil port on the Black Sea. The city was placed under the direct control of the General Government of Georgia only in 1903.
After becoming a Soviet State, in 1921, Ajara - with its centre in Batumi - was declared an Autonomous Republic. It retains this status to the present day. During the Soviet era, however, Batumi lost its significance and was a fairly ordinary Soviet town.
Since 2000s, Batumi has been a city in search of its past. It is once again becoming an important Black Sea city, this time as a tourist destination.