On March 13, 1968 the Atlantic Richfield Oil Company, known as ARCO, struck oil on the North Slope of Alaska near the Arctic Ocean. Shortly after it became known that it was one of the largest oil fields in the world. Barges can come into Prudhoe Bay only six weeks each year. Men who work on oil rigs are called "roughnecks". They wear hard hats to protect their heads in case of accidents. Oil is pumped through the Transalaska Pipeline from Prudhoe Bay to Valdez, Alaska to be pumped into tankers and taken to refineries.