Complex sentence: The Hanford nuclear site, aluminum production, and the shipbuilding industry contributed to such a rapid increase in regional demand for electricity that by 1943, fully 96 percent of Columbia River electricity was being used for war manufacturing.
Split into simpler sentences: The Hanford nuclear site, aluminum production, and the shipbuilding industry contributed to a rapid increase in regional demand for electricity. By 1943, fully 96 percent of Columbia River electricity was being used for war manufacturing.