Complex sentence: By 1957, the Great Northern Railway no longer had a need for the Casselton reservoir, and they deeded the of land, which encompassed that body of water, to the City of Casselton.
Split into simpler sentences: By 1957, the Great Northern Railway no longer had a need for the Casselton reservoir. They deeded the of land, which encompassed that body of water, to the City of Casselton.