Before the United States entered World War II after the bombing of Pearl Harbor in December 1941, ninety-five percent of the crude oil delivered to East Coast refineries traveled by tanker ships, and ninety percent of that oil came from Texas fields. Beginning in February 1942, German submarines sank many U.S. tankers bound from the Gulf of Mexico to the East Coast, prompting Secretary of the Interior Harold Ickes to develop a plan for a massive overland oil pipeline. Built under War Emergency Pipelines, Inc., the Big Inch was the largest pipeline in history up to that time, measuring twenty-four inches in diameter and running from Longview to Norris City, Illinois, and eventually to refineries in the East. Its effect on the war effort was tremendous, allowing the safe and timely transport of oil products vital to the Allies. At the height of wartime service, the 1,476-mile line delivered more than 300,000 barrels of oil each day, and after the war it remained in use after conversion to a natural gas pipeline.