 On March 1, 2008, Chita Oblast merged with Agin-Buryat Autonomous Okrug to form Zabaykalsky Krai.The territory that made up the former Chita Oblast was first explored by Cossacks led by Pyotr Beketov in 1653.People began to move into and develop the area in order to strengthen Russia's border with China and Mongolia, extract mineral resources, and build the Trans-Siberian Railway.