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%.