Complex sentence: During the California Gold Rush, as many people from all over the world traveled to California to mine for gold, tens of thousands took a steamboat that was operated by the Accessory Transit Company and was directed by Cornelius Vanderbilt.
Split into simpler sentences: During the California Gold Rush, as many people from all over the world traveled to California to mine for gold. Tens of thousands took a steamboat that was operated by the Accessory Transit Company and was directed by Cornelius Vanderbilt.