Facebook Friend Ken Gardner passes on this graphic from the American Enterprise Institute:

According to the U.S. Department of Labor Bureau of Labor Statistics, the lowest quartile (“20 percent” in plain English) of households by pretax income in 2013 went to $17,882, the second quintile went to $34,957, the middle quintile went to $57,967, the fourth quintile went to $95,337, and obviously the highest quintile goes above that.