Plovdiv reached an agreement that the Principality of Bulgaria and Eastern Rumelia had a common government, Parliament, administration, and army. Today 6 September is celebrated as the Unification Day and the Day of Plovdiv. After the unification, Plovdiv remained the second most populous city in Bulgaria after the capital Sofia. The first railway in the city was built in 1874 connecting it with the Ottoman capital, and in 1888, it was linked with Sofia. In 1892 Plovdiv became host of the First Bulgarian Fair with international participation which was succeeded by the International Fair Plovdiv. After the liberation, the first brewery
Plovdiv is the second or the third-largest cosmopolitan city inhabited by Bulgarians, after Sofia and possibly Varna. According to the 2001 census, out of a population of 338,224 inhabitants, the Bulgarians numbered 302,858 (90%). Stolipinovo in Plovdiv is the largest Roma neighbourhood in the Balkans, having a population of around 20,000 alone; further Roma ghettos are Hadji Hassan Mahala and Sheker Mahala. Therefore, the census number is a deflation of the number of Roma people, and they are most likely the second-largest group after the Bulgarians, most of all because the Muslim Roma in Plovdiv claim to be of Turkish ethnicity