Complex sentence: After the Donner Party's disastrous winter of 1847 in the Sierras which happened just before the news of California gold became public, a loose group arrived in October 1849 at the Great Salt Lake.
Split into simpler sentences: After the Donner Party's disastrous winter of 1847 in the Sierras which happened just before the news of California gold became public. A loose group arrived in October 1849 at the Great Salt Lake.