. The OCA began when eight Russian Orthodox monks established a mission in Alaska, then part of Russian America, in 1794. This became a diocese of the Russian Orthodox Church after the United States purchased Alaska from Russia in 1867. By the late 19th century, the Russian Orthodox Church had grown in other areas of the United States due to the arrival of immigrants from areas of Eastern and Central Europe, many of them formerly of the Eastern Catholic churches ("Greek Catholics"), and from the Middle East. These immigrants, regardless of nationality or ethnic background, were united under a single North American diocese of the Russian Orthodox Church.