Complex sentence: Perhaps because of the pressure of this European encroachment, some Tlingit appealed to the Russian Orthodox Church, which had given services in northern settlements in local languages since 1800 and 1824.
Split into simpler sentences: Perhaps because of the pressure of this European encroachment, some Tlingit appealed to the Russian Orthodox Church. It had given services in northern Tlingit settlements in local languages since 1800 and 1824.