Visit the U.S. Bureau of Labor Statistics' (BLS) Earnings page for current and historical data on the earnings of American employees. The data can be disaggregated in a number of ways; including by demographics; education; occupation; and union membership.
ProQuest Statistical Datasets features U.S. earnings data. Try searching for the following phrases: labor and employment; current employment statistics; national compensation survey; state and local employment; and wage rates hourly.