Oklahoma's earliest manufactures were based on agricultural and petroleum production. As late as 1939, the food-processing and petroleum-refining industries together accounted for one-third of the total value added by manufacture. Although resource-related industries continue to predominate, manufacturing was much more diversified in 1997. The total value of shipments of manufactured goods was more than $38 billion, with only 10% from fuel extraction and refining, and 10% from food. In 1997, four Fortune 500 companies were headquartered in Oklahoma: Fleming, Phillips Petroleum, Williams, and Mapco.
Earnings of persons employed in Oklahoma increased from $48.3 billion in 1997 to $51.1 billion in 1998, an increase of 5.9%. The largest industries in 1998 were services, 24.6% of earnings; state and local government, 12.4%; and durable goods manufacturing, 10.4%. Of the industries that accounted for at least 5% of earnings in 1998, the slowest growing from 1997 to 1998 was state and local government, which increased 2.8%; the fastest was services, which increased 6.8%.