There is very little data about the distribution of wealth in America. There is one source, the Survey of Consumer Finances, sponsored by the Federal Reserve Board, that does provide data from 1983.
These data suggest that wealth is concentrated in the hands of a small number of families. The wealthiest 1 percent of families owns roughly 34.3% of the nation's net worth, the top 10% of families owns over 71%, and the bottom 40% of the population owns way less than 1%.
The distribution of wealth is much more unequal than the distribution of income, especially when focussing on the bottom 60% of all households. The bottom 60% of households possess only 4% of the nation's wealth while it earns 26.8% of all income.
US wealth distribution: 10% of US citizens own 70.9% of all US assets.
Top 1% own 38.1%
Top 96-99% own 21.3%
Top 90-95% own 11.5%
And it gets much uglier as you proceed downward. Bottom 40% of population has 0.2% of all wealth.