Complex sentence: The second and most dramatic boom and bust resulted from the Klondike Gold Rush, which ended the depression that had begun with the Panic of 1893; in a short time, Seattle became a major transportation center.
Split into simpler sentences: The second and most dramatic boom resulted from the Klondike Gold Rush, which ended the depression that had begun with the Panic of 1893. In a short time, Seattle became a major transportation center.