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 Province capital is the city of Plovdiv; other towns include Karlovo, Sopot, Klisura, Kalofer, Hisarya, Saedinenie, Rakovski, Brezovo, Stamboliyski, Krichim, Perushtitsa, Sadovo, Parvomay, Asenovgrad, Laki, Katunica, Yiagodovo. Plovdiv Province had a population of 715,904 (715,816 also given) according to a 2001 census, of which were male and were female. As of the end of 2009, the population, announced by the Bulgarian National Statistical Institute, numbered 701,684 of which are over 60 years of age. The following table represents the change of the population in the province after World War II: Total population (2011 census): 683 027<br> Ethnic groups (2011 census): Identified