The settlement quickly became one of the main economic centres on the Pacific coast of the Russian Empire. It became Russia's main Pacific harbour (replacing Petropavlovsk) in 1855 after the Siege of Petropavlovsk of 1854. It was granted town status and renamed Nikolayevsk-on-Amur in 1856, when Primorskaya Oblast was established. Admiral Vasily Zavoyko supervised the construction of a naval base in Nikolayevsk-on-Amur.