The story of oil production in California began in the late 19th century. In 1903, California became the leading oil-producing state in the US, and traded the number one position back-and forth with Oklahoma through the year 1930. As of 2012, California was the nation's third most prolific oil-producing state, behind only Texas and North Dakota. In the past century, California’s oil industry grew to become the state’s number one GDP export and one of the most profitable industries in the region. The history of oil in the state of California, however, dates back much earlier than the 19th century. For thousands of years prior to European settlement in America, Native Americans in the California territory excavated oil seeps. By the mid-19th century, American geologists discovered the vast oil reserves in California and began mass drilling in the Western Territory. While California’s production of excavated oil increased significantly during the early 20th century, the accelerated drilling resulted in an overproduction of the commodity, and the federal government unsuccessfully made several attempts to regulate the oil market.