Kosta Rankov is a lawyer, liberal Radoslavist by party affiliation. He was born in Provadia in 1865. He moved to Varna in 1882. He took an active part in the social, cultural and business life of the town.
He is among the founders of "Sila" and "Galata" JSCos. He had been an MP. In both his terms in office he worked diligently for the urban development of the town. At that time the improvement of water supply became a major issue again. There were debates on the possibility to capture and bring water from the springs and special survey was commissioned to an engineer. Measures were taken to improve the conditions for holiday-makers. The councillors discussed the suggestion to point out an area within the town limits for housing the poor roofless people. This concerned the poor, settled down in town for at least 10 years. A time limit for the construction works was set - one year. Summer and evening schools were opened and supported, free canteens operated for the poor children, Mother Society was give land for free to build its own school.
Because of lack of finances, short-sightedness and political struggles, some of the resolutions of the Municipality Council were suspended, the implementation of others was left to the future.
Kosta Rankov continued his cultural and charity activities in the years when he was no longer mayor. In 1911 he built with his own money "Rankov Salon", hosting theatre performances and, after World war One, it became one of the most prestigious movie salons in town. It was built under the design of a Romanian architectural bureau, with sculpture elements by Kiril Shivarov, a sculptor from Varna.