Between 1945 and 1980, the wealthiest 10 percent of our society received only around a third of national income. Since 1980, income distribution has returned to levels of inequity not seen since the Gilded Age at the turn of the last century. This was a period when our economy was dominated by robber barons like the Rockefellers. Now, as then, the top 10 percent capture about half of all national income generated in the United States.
For more context on the causes of rising inequality in the United States, check out the brief Was the American Economy Ever Great?